Some are using rubber no slip shelf mats.
That's what I"m planning to use. If I can remember.. I got so excited about lock down last time I forgot. lol...
I also have seen someone made little cups out of paper towels or something like that.
I also use the mat in the brooder for the first few days.
And it's machine washable. I got mine at Wal Mart in the contact paper area.