Preheat oven to 450 degrees Fahrenheit. Prepare a rimmed baking sheet and drizzle with olive oil.
Bring a large pot of water to a boil; add potatoes. Boil 20 minutes or until tender and potatoes can easily be pierced with a fork. Drain and set aside to cool slightly.
Mince garlic and chop green onions and dill. Melt 3 Tbsp butter.
Place boiled potatoes on the prepared baking sheet, allowing space between each. Using the base of a wide, round glass (or another flat object for pressing the potatoes), gently press the potatoes until they are approximately 1/2 inch thick. If the potatoes are sticking to your glass, spray your glass with cooking spray, or drizzle with olive oil. There is some wiggle room here, but do not press all the way down to the baking sheet. Repeat until all potoatoes are smashed.
Brush the smashed potatoes generously with the melted butter. Sprinkle with the minced garlic, salt and pepper.
Roast in the oven for 18-20 minutes, or until potatoes are crispy and browning on the edges. Remove from oven and transfer to a serving dish.
Sprinkle generously (really!) with chopped dill, chopped green onions, and additional salt and pepper, if desired.