I can think of two types.
1) A rectangle with corners cut out and tied together (looks like a cross before it's tied) that forms a hot pad around the casserole dish. It would be made to fit a single size casserole
2) Same as above with longer sides to use as handles. The photo I saw had wooden spoons used as handles.
Here's one that uses dowels
http://jolenlovestosew.blogspot.com/...-tutorial.html
Here's one that holds a wooden spoon.
http://littlebirdiesecrets.blogspot....ial-guest.html
there are plenty more if you google "casserole carrier tutorial"