In short, remove the ends of the bread. Crumble into tiny pieces coarsely. For every slice, add 1 tbsp of fevicol or any thick glue. Keep mixing with a plastic spoon or hands. Add acrylic paint to get your preferred color. Don't worry if the dough sticks to your hand, eventually it becomes like a chapati/roti dough. You can wear plastic gloves too instead. Keep kneading. Add a bit of corn flour if the dough is sticky or add another slice of bread. That's it. You're almost done. When you get the flexible dough, store it immediately in a plastic cling wrap or zip lock bag and store in the fridge if not using immediately.
If the dough is kept out, it loses its moisture and becomes hard to work with. Go on and make your favorite toys out of the clay. Let it air dry for atleast 24 hours. No need to bake. Only air dry. Once it is completely dry, paint a coat of clear varnish or clear nail polish to protect it from molds. Ta da!! Your kids will love to play with this dough and make their favorite characters out of it.
You can have a look at the "How to" video below or just visit the below link before you make it. I do not want to repeat what someone has already done on the web ;)