My corners always come out a little rounded on the edges. How can a get a mored squared off edge?

i use setting ganache under my fondant (like Planet Cakes) and it gives a nice crisp base to apply the fondant. Also, using TWO fondant smoothers seems to work wonders for me.

What if you are using butter cream and not fondant?

this video is suuuuper helpful if you are doing a square buttercream cake

What brand of pans are you using? That makes a difference on the sharpness of your edges. Magic Line pans have nice straight sides. Wilton not so much. HTH.

My pans are Wilton Thanks, I'll be on the lookout for better ones next time I plan on doing square. Thank you!