My standing sub plan has been Susie’s: groups of 2-3 kids develop and practice stories in ten minutes, drawing illustrations on a white board. Then they present to the class (everyone must talk). You can tweak it by asking them to re-tell a former story with changes, or to use specific structures.
Today we practiced the sub plan. It was great: I was off the hook (refusing valiantly to offer any vocabulary or other help) and I got to listen to the kids! Now I have a grade to enter, and I know what the kids have learned. Such a deal.