I actually stole this idea from Mr3s current favourite show, Mister Maker. We used soup mix, but you could use lots of different things, dry lentils, rice, couscous, anything that is going to give you a unique texture and that is fun to run through your hands.
I just printed out some basic shapes from the internet. Keep them simple as you’re going to cover up any detail anyway. Smear the area with some craft glue and attach an goggly eye. Then let the kids sprinkle the mix over the rest of the glue area to completely cover it. Gently shake off any excess into the bin. These took about 24 hours to dry. Once fully dry, cut out. We created a simple background with some coloured paper and put them in $2 Ikea frames.