web developers make accordion lists using JavaScript, JQuery and CSS3… however JQuery doesn’t work well on Ionic 3. Twitter Bootstrap accordion list is based on JQuery animation as well.
In my opinion, CSS3 accordion is the best way although it will take some time to learn how it works.
Or you can try to combine it with original Ionic components.
another solution is using Angular’s ngClass to dynamically add & remove CSS3 class on accordion list item. so once you click on accordion list item, angular will add a css3 class of display: inline or height: 350px to make the item expand its content.