Found this recipe here:
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Sawdust Clay
2 cups sawdust
1 cup flour water Mix two parts sawdust with one part water. Add water, until the mixture is stiff, but pliable. If dough is too crumbly, add a little more flour. Dump the mixture on a newspaper-covered table. Knead until it reaches an elastic consistency. The dough may then be molded into any shape desired, then dried in the sun. As it dries, it will become extremely hard. After drying, it can be sanded and painted, or simply painted, depending on preference. Once the paint dries, an acrylic finish will make creations shine.
I haven't tried this yet, but intend to. The other recipe I saw called for wallpaper paste - which would mean something extra to buy. This one uses flour, which most people already have. If it works as described, I can think of several ways to use it, right off the top of my head - as long it doesn't turn out to be brittle, that is, but even if it is, I can still think of a use or two..
JOAT The Truth Shall Set Ye Fret