Combine the salt, sodium carbonate and bicarbonate of soda in the plastic bag.
Use the popsicle stick to carve a little face into the apple, pushing in the stick to make two eyes, a nose and a mouth. Insert the popsicle stick into the top of the apple to create a handle.
Put the apple in the plastic bag and shake it around so the apple becomes covered.
Keep the open bag with the apple in a warm dry place. Observe the apple over a couple days until it is completely mummified and wrinkly. Remove the apple from the bag and brush off any powder residue.