I am slowly closing in on what a purist would call a genuine slider.  Start out with the onions under the burger patty and let them cook on medium heat for a while.  (I think from here they are covered and steamed done to be perfect sliders.)  I flipped mine over and added the pickles and cheese and placed the buns just so.   I think they came off close enough for me to call them a win!  Of course, they need mustard and a pile of fries.I get quite a bit of use from that cast iron griddle that those burgers cooked on today.  Pretty sure it’s from the Lodge foundry.  I think they’re the only US maker of cast iron items like that.  I actually have a two burner griddle that builds into the Jenn-Air stove top, and an open flame grill section as well, but they are an enormous PITA to maintain.  The Lodge item works just as well and stores away easily so I have my four burners back again.  These days I drool over the new stoves in the appliance stores but we have managed to get by so far.  Maybe with a kitchen remodel one of these days, much as I hate the mess and the bother.