Step 1: Go to 'Layout' > click the 'Add a Gadget' link in the sidebar area and select 'HTML/JavaScript' gadget from the pop-up window.

Step 2: Copy the following code and paste it inside HTML/JavaScript gadget

<style type="text/css">
ul.featured-widget-list,ul.featured-widget-list li{margin:0;padding:0;list-style:none;position:relative }ul.featured-widget-list li{display:none}ul.featured-widget-list li:nth-child(1){display:block;line-height:0}ul.featured-widget-list img{border:0;width:100%;height:auto}ul.featured-widget-list .featuredbg{width:100%;height:100%;position:absolute;z-index:2;left:0;top:0;opacity:.6;background-image:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDWpUjF-LzA3B-Te4XcKnxWzqKLXG1ch_iP9GTHPLJumGz64Xxp6ljVu_i87RlU4QtK2dR2KBMI1WdXPoF96UBHIs03cRfxn8_rskblb-OGRyiuARAkENmZWUREuJxf-MpavtzgZyc8T0/s400/overlay-bg.png);background-position:0% 100%;background-repeat:repeat-x}ul.featured-widget-list .featuredbg:hover{opacity:.1}ul.featured-widget-list h5{position:absolute;left:0;right:0;text-align:center;bottom:10px;z-index:2;color:#fff;margin:0;text-transform: capitalize;padding:10px 20px;line-height:1.9em;letter-spacing:0.3px;font: 600 16px 'Abel', sans-serif;overflow:hidden}ul.featured-widget-list li:hover h5{bottom:30px}ul.featured-widget-list .featured-meta{font: 11px 'Abel', sans-serif;letter-spacing:0.3px;position:absolute;bottom:0;left:0;right:0;text-align:center;z-index:2;color:#fff;opacity:0}ul.featured-widget-list h5, ul.featured-widget-list .featured-meta {-webkit-transition: all 0.3s;-moz-transition: all 0.3s;-o-transition: all 0.3s;transition: all 0.3s;}ul.featured-widget-list li:hover .featured-meta{bottom:20px;opacity:1}.feat-buttons{position:absolute;top:50%;left:0;z-index:5;width:100%}
.feat-buttons a{text-indent:-9999px;margin:0 7px;width:15px;height:15px;padding:5px;background:#000;-ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=60)";filter: alpha(opacity=60);-moz-opacity:0.6;-khtml-opacity:0.6;opacity:0.6;position:relative;-webkit-border-radius: 50%;-moz-border-radius: 50%;border-radius: 50%;}.feat-prev{float:left;}.feat-next{float:right;}.feat-buttons a.feat-prev::before, .feat-buttons a.feat-next::before{content:"";width:0;height:0;border-width:6px 7px;border-style:solid;border-color:transparent #fff transparent transparent;position:absolute;top:50%;margin-top:-6px;margin-left:-11px;left:50%}
.feat-buttons a.feat-next::before{border-color:transparent transparent transparent #fff;margin-left:-3px}
</style>
<div id="featuredbwidget"></div>
<link href='https://fonts.googleapis.com/css?family=Abel' rel='stylesheet' type='text/css'/>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js" type="text/javascript"></script>
<script type='text/javascript'>
//<![CDATA[
featuredbwidget({
listURL:"https://atozbloggertips.blogspot.com/",
featuredNum:9,
listbyLabel:false,
feathumbSize:350,
interval:3000,
autoplay:true,
featuredID:"#featuredbwidget"
});
function featuredbwidget(a){(function(e){var h={listURL:"",featuredNum:3,featuredID:"",feathumbSize:300,interval:5000,autoplay:false,loadingFeatured:"nextfeatured",pBlank:"https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5gIiGeRIpTDkB4KHtwv6LPlbEMcVAOhhIDcfO_DlBA6PNkhUSnSyVZLXkHqZ9rFEu4vNS7wxErxDuWV671GdmjbiTm8XONeYte7gaaZdikHxDHKBU-eFifecCdBHm7pzu4L-vd9aLFf8/s500/no-image.png",byMonth:["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"],listbyLabel:false};h=e.extend({},h,a);var g=e(h.featuredID);var d=h.featuredNum*200;g.html('<div class="featslider"><ul class="featured-widget-list"></ul><div class="feat-buttons"><a href="#" class="feat-prev">Prev</a><a href="#" class="feat-next">Next</a></div></div>');var f=function(w){var q,k,m,u,x,p,t,v,r,l="",s=w.feed.entry;for(var o=0;o<s.length;o++){for(var n=0;n<s[o].link.length;n++){if(s[o].link[n].rel=="alternate"){q=s[o].link[n].href;break}}if("media$thumbnail" in s[o]){u=s[o].media$thumbnail.url.replace(/\/s[0-9]+\-c/g,"/s"+h.feathumbSize+"-c")}else{u=h.pBlank.replace(/\/s[0-9]+(\-c|\/)/,"/s"+h.feathumbSize+"$1")}k=s[o].title.$t;r=s[o].published.$t.substring(0,10);m=s[o].author[0].name.$t;x=r.substring(0,4);p=r.substring(5,7);t=r.substring(8,10);v=h.byMonth[parseInt(p,10)-1];l+='<li><a href="'+q+'"><div class="featuredbg"></div><img class="featuredthumb" src="'+u+'"/><h5>'+k+'</h5></a><div class="featured-meta"><span class="fdate"><span class="fday">'+t+'</span> <span class="fmonth">'+v+'</span> <span class="fyear">'+x+'</span></span> - <span class="fauthor">'+m+"</span></div></li>"}e("ul",g).append(l).addClass(h.loadingFeatured)};var c=function(){e(h.featuredID+" .feat-next").click()};var b=function(){e.get((h.listURL===""?window.location.protocol+"//"+window.location.host:h.listURL)+"/feeds/posts/summary"+(h.listbyLabel===false?"":"/-/"+h.listbyLabel)+"?max-results="+h.featuredNum+"&orderby=published&alt=json-in-script",f,"jsonp");setTimeout(function(){e(h.featuredID+" .feat-prev").click(function(){e(h.featuredID+" .featslider li:first").before(e(h.featuredID+" .featslider li:last"));return false});e(h.featuredID+" .feat-next").click(function(){e(h.featuredID+" .featslider li:last").after(e(h.featuredID+" .featslider li:first"));return false});if(h.autoplay){var i=h.interval;var j=setInterval(c,i);e(h.featuredID+" .featslider li:first").before(e(h.featuredID+" .featslider li:last"));e(h.featuredID+" .featslider").hover(function(){clearInterval(j)},function(){j=setInterval(c,i)})}e("ul",g).removeClass(h.loadingFeatured)},d)};e(document).ready(b)})(jQuery)};
//]]>
</script>

listURL: replace "https://atozbloggertps.blogspot.com" with your blog URL

featuredNum: add the umber of posts to display in the slider

listbyLabel: if you want to display posts by category/label, such as the tag fashion, it will be written as listbyLabel:"fashion"

feathumbSize:the size or dimension of the image in pixels

interval: time taken to change the slides position in milliseconds

autoplay: replace true with false if you do not want the slides to change automatically.

Step 3: Once yo are done with these settings, click the 'Save' button.

Now, this code is for a slide widget which means that instead of just a random list of Featured Posts, you get to display them with images and you can include effects too. You can also control how many slides should be shown because it just would not be prudent to feature.