Preheat oven to 425˚F. Line a rimmed small baking pan with foil.
Melt butter and combine with salt, pepper and chopped thyme. Set aside.
Scrub potatoes and pat them dry. (Peel potatoes if desired.)
Cut slits in the potatoes leaving the bottom intact: Line potato up between ¼-inch thick wooden spatula handles or chop-stick on a cutting board or use Hasselbach cutting board. Cut potatoes crosswise, straight down at ⅛ to ¼-inch intervals.
Brush potatoes, top and bottom, with seasoned butter mixture, using about half of the mixture. Place potatoes on prepared rimmed baking pan.
Bake 30 minutes. During baking potatoes will fan out but press sides to increase the gaps. Brush with remaining butter mixture and sprinkle ground almonds. Return to oven and bake for additional 20 to 30 minutes.
Technique works with a variety of potatoes even sweet potatoes and other vegetables such as zucchini. Equipment required: 2 spatulas with ¼-inch thick wooden handles or similar set of ¼-thick sticks such as chop sticks; or a Hasselback Potato cutting board.