Preheat griddle to medium-high. Place beef on the Blackstone, spaced apart. Use a burger press to smash each flat and thin, twisting slightly. Sprinkle a little kosher salt, pepper, and seasoning blend on burgers. Flip after 2 minutes with spatulas. Note: Place a piece of parchment paper between beef and burger press before smashing to prevent sticking.
Sprinkle a little more kosher salt, pepper, and seasoning blend on burgers and top each with a slice of cheese. Cook 1 to 2 more minutes until cheese is melted.
Place buns, cut side down, on griddle for 20 seconds to toast them.
Assemble each burger with a burger patty on the bottom bun, some tartar sauce, top with another patty, more tartar sauce, lettuce, pickles, and then add the top bun.