Preheat oven to 500° F.
Rinse and gently scrub potatoes. Place potatoes on a rimmed baking sheet. Pour 3/4 cup water into the baking sheet and tightly cover with aluminum foil. Bake for 30 minutes or until potatoes poke easily through the aluminum foil with with a sharp pointed knife or tines of a fork. Remove aluminum foil and blot any remaining water in pan dry with a paper towel.
While potatoes are cooling, melt butter in a sauce pan. As soon as butter is melted, add garlic and sauté until light golden brown (about 1 minute). Remove from heat and stir in thyme.
Optional step: Using a small pointed knife (such as a paring or steak knife), poke about 4-5 small vertical slits around sides of potatoes (this helps potatoes to smash more evenly). Drizzle oil over the potatoes, rolling the potatoes to coat. Evenly space potatoes on baking sheet. Using another baking sheet, press down firmly over potatoes, flattening potatoes until they are 3/8 to 1/2-inch thick (alternatively, a potato masher or flat bottom of a drinking glass may be used, smashing one potato at a time).
Spoon butter, garlic and thyme mixture over potatoes. Season to taste with salt and pepper. Return potatoes to oven (uncovered) and bake for another 5-10 minutes or just until potatoes and garlic are lightly browned (be careful not to burn garlic). Serve immediately.