First, mix together –
1/2 cup toilet paper (24 grams dry, 110 grams wet)
1/2 cup Joint Compound (200 grams)
1/2 cup Elmer’s glue (130 grams)
1/2 cup corn starch (70 grams)
3 tablespoons mineral oil (or use linseed oil or any vegetable oil)
1/2 cup all-purpose flour (70 grams) to start

Then, add up to 3/4 cup (100 grams) all-purpose flour and mix.

From: http://www.ultimatepapermache.com/new-air-dry-clay-recipe