how to bake a sweet potato fast
1 Don't preheat the oven. 2  Prick your sweet potatoes each 2-3 time with a fork, then place them directly on the oven rack in the middle of the oven, above the foil. 3  Turn the oven on to 425. 4  Bake for 45 minutes for sweet potatoes/yams that are 2-3 inches in diameter. For super large sweet potatoes, bake for an hour and 15 minutes. 2  After the time has elapsed, don't open the oven but turn it off. 3  Let the sweet potatoes sit in the oven for at least 30 minutes but up to an hour. 4  Remove from the oven and eat immediately, or remove the skin and store in a container in the fridge.