Reddit reviews Victorinox Turner 5' X 6" Hamburger, Stiff, 3 Sides, Beveled with peggable Sheath

I have this one and it is amazing.

I'd probably be comfortable doing 4 at a time, but so far I've only done two. If you're gonna be doing this relatively often invest in a good, solid, non-slotted spatula. Something like this (I haven't used that one, but that's the idea). I'll throw two balls of meat on the steel, then press them one at a time (each for about 10 seconds) using another spatula (or wooden spoon, whatever) to press down on the big spatula.

The baking sheet idea is intriguing, just be careful and use a couple oven mitts - that pan will get real hot! One thing to watch out for is when you pull it off, hopefully the meat doesn't want to come with it. I sometimes have that problem with just a spatula - in those cases I usually just keep pressing for a few seconds longer.