Always go for ground sirloin for smash burgers. Hot and fast, about 3 minutes top. Portable blackstone does a great job. I aim for a Steak’n Shake burger. Ground salt and pepper are the only seasonings. Maybe a little olive oil on the grill before I place the burger on it.
Another tip is to place the spatula on the burger with one hand, and smash it down with the beer bottle that’s in your other hand.