Three Corners Completed

Just finished the third corner – one to go; however, I’m thinking I may have to redo the first corner (upper left) because when I’ve finished the fourth I think I’m going to be short on the first side and the panel isn’t going to be square – I might be off as much as 3/4″! Here’s hoping I’m not. 3/8″ – 1/2″ I can fudge when adding the outside border, but more than that will want a redo.