To make the crab in a seashell, roll up a bathtowel, starting in the corner. Then curl the roll into a seashell. You might need to prop it against something to keep it from uncurling.
Then take a washcloth and roll it from both sides into the middle. Turn it over and then turn each of the ends under about an inch and a half to reveal the claws. Fold it in half and insert your crab into the seashell.