Start by selecting firm, green, and unripe plantains. Slice off the very tips.
Peel the plantains by cutting the peel into strips and pulling them away or slicing along the length and using a spoon to separate the peel from the flesh.
Cut the peeled plantain into discs, about ¼ to ½ inch thick.
Heat oil in a skillet or deep fryer to medium heat.
Add the plantain slices to the skillet and season with salt, pepper, and garlic powder.
Fry the plantains on each side for 1-2 minutes, then remove and drain on paper towels.
Flatten the fried plantains on a flat surface to your desired thickness.
Return the flattened plantains to the oil and fry until golden brown.
Remove the tostones from the oil, drain on paper towels, and season with additional salt to taste.
Combine minced garlic, mayonnaise, and lemon juice for the dipping sauce in a small bowl and mix well. For the best flavor, prepare the sauce a little ahead of time.