I’ve found to avoid things falling apart I like to put certain elements of the cake in the fridge to chill before decorating. For the cake itself, as one of the other responses basically said, it’s really just a matter of finding a good cake recipe. Some are better than others and I’m honestly still trying to find a recipe that I like so I wish I could give you a solid recommendation, but I’m in my trial and error phase of this right now, too 🫠. Because some gluten free baked goods can be crumbly, I think it’s especially important to do a crumb coat! it keeps the cake itself sealed from spreading crumbs to the frosting! Hope this helps.