I've made a fitted crib sheet before and typically it's not too bad, especially when you are using a lightweight sheeting fabric. My most recent challenge came when a client asked for 2 fitted crib sheets out of minky dot fabric. I was concerned about the stretchiness and thickness of the fabric. I referred to Amy Butler's "little stitches for little ones" book for instructions. I found them very easy to follow. I made both sheets in one evening and I think they turned out great! I tested them in our nursery (more to come on that later).