Line an 8-inch square baking pan with parchment paper or wax paper. Set aside. You can also use a granola bar pan set on a small cookie sheet for stability. Clear some space in the freezer for this pan—you will need it later.

In a medium, microwave-safe bowl (large enough to add oats later), add peanut butter and maple syrup. Whisk together until well mixed. Heat in 20-second increments in the microwave until warm, fragrant, and bubbles begin to form. Whisk in between heating increments. *Stovetop instructions in Notes.

Add oats to the peanut butter mixture. Using a rubber spatula, stir and fold until thoroughly combined. Pour this mixture into the prepared baking pan. Using the rubber spatula, smooth into an even, tightly packed layer. If using a granola bar pan, evenly distribute mixture into the crevices in the pan. Using a small spoon, press down into a very tightly-packed layer.

Freeze for 25-35 minutes, or until firm and completely chilled. Slice into 18 bars (3 columns by 6 rows), or release bars from granola bar pan. Enjoy! Storing instructions below.