No special tools are needed for these easy smash burgers.  Use a spatula and a piece of parchment paper.  If you really want extra leverage, use another spatula, wooden spoon, or a bench scraper to press down on the smashing spatula.  We love using a steaming dome for our blackstone (you can use any lid or cover, or even an upside down pan if you don't have one) or buy one here.