I think I got the pattern from the craft that I offered. I believe I originally found this idea and the patterns in one of the series of monthly idea books by The Education Center: Mailbox Magazine.
This is easy prep and a great fine motor, eye-hand coordination activity. Actually, you could let the kiddos cut the 'grass' at the top of the 9x12 piece of construction paper. I'd probably prep the slits for weaving. But you could have the paper folded with lines drawn for the older kiddos to cut. Snakes in the grass are a lot of Fun with Friends at Sssstorytime! There are more great posts on the Flannel Friday Roundup. Check out the wonderful resources on the Flannel Friday Pinterest Boards. If you want more info about Flannel Friday here's the link for the official Flannel Friday blog.