Up until this point I was pinning all of them then sewing a batch. I find that since they do occasionally get chewed up, it is more time effective for me to hand stitch a batch really quick. There does not need to be a lot of stitches to hold it together, and if you can sew on a button you can totally do this! If you are not able to sew a button - consider this idea with safety pins instead of the thread (this was how we first did it!)
The example below, is the same for all shelves and pans for the Critter Nations, and will work for any other cage that has inserts. I have chosen to use the pan with the cut out for the example because that is the only different or 'tricky' part. (See Step 6)