Heat about 2 cups vegetable oil over high heat in a pot. The oil should cover the bottom of the pot. You can use a skillet but a pot or saucepan prevents oil from splashing everywhere.
While the oil heats up, peel 4 unripe green plantains and cut them into three to four even-sized pieces. For a tutorial on how to peel plantains, refer to the full blog post.
Test the temperature of the oil with one plantain piece to make sure it’s hot enough. If the oil is ready, it will bubble and begin frying the plantain.
Add all the plantains to the oil and cook for about 6 to 8 minutes until golden brown. If the oil doesn't completely cover the plantains, flip them occasionally to cook all sides. While the plantains cook, line a plate with paper towels.
Once the plantains are golden transfer them to a cutting board. Smash the plantains with the bottom of a jar, cup, or plate. You may need to use a butter knife or spatula to carefully scrape each tostone off the bottom of whatever you smashed them with.
Working in batches, add the smashed plantains back to the oil to fry for a second time for about 1 minute on each side.
Take the crispy tostones out once they’re golden brown and transfer them to the paper-towel-lined plate.