Gwt: Cls Issue: More Than 0.25 (Desktop)

So in Google Webmaster Tools/Core Web Vitals I am seeing all kinds of issues lately:

Mobile:

0 poor URLs
5,265 URLs need improvement
0 good URLs
Desktop:
900 poor URLs
4,365 URLs need improvement
0 good URLs
Anyone on here a pro at fixing stuff like this? According to web.dev:

The most common causes of a poor CLS are:

  • Images without dimensions
  • Ads, embeds, and iframes without dimensions
  • Dynamically injected content
  • Web Fonts causing FOIT/FOUT
  • Actions waiting for a network response before updating DOM

All my images have dimensions. Not sure how to check for the other things. Example bad page: https://fastdecals.com/shop/aftermarket-logos/f-logos/fastdecals.com-decals/fastdecals.com-pair-decal-sticker-31.html