Preheating: Add oil to a frying pan and set on low heat. You’ll need about 1 inch of oil in the pan. 

Peeling and Slicing: Cut the ends off the plantain, cut 4 slits diagonally into plantain. Stick a knife blade just under the skin and begin to pry the skin off. Peel each section, being careful not to remove any of the flesh. Cut crosswise into 1 1/2 inch slices. 

First Frying: Fry the plantain slices on low heat for about 3 minutes on each side. Remove and drain on paper towels.  Remove from oil, drain on paper towels and salt immediately (so the salt sticks to the tostones). 

Smashing: Place one slice on a cutting board and use a small plate or a large glass measuring cup to mash the plantain to about a 1/2″ to 1/4″ thickness, depending on your preference. If you’re making tostones cups, you’ll need to use the special masher. Spray the cup with a little cooking spray to make it easy to remove the mashed cup. 

Second Frying: Increase the heat to medium low and cooke the plantain discs or cups until golden, about 2-3 minutes total.