Combine the marinade ingredients in a small bowl and stir to dissolve. Place in a plastic bag or container.

Trim excess fat from the lamb and butterfly it into uniform pieces. Season all sides liberally with kosher salt, then place the butterflied lamb in the plastic bag with the marinade.

Remove the lamb from the fridge, drip off any excess marinade from the bag, and pat the lamb dry with paper towels. Allow it to sit at room temperature for 30 to 60 minutes before cooking. Insert a probe thermometer into the thickest part of the butterflied lamb to monitor the internal temperature.

Prepare the grill for two-zone cooking (one direct heat zone and one indirect heat zone) and maintain a temperature of around 300°F on the indirect side. Add wood chips or chunks to the charcoal or smoker box for extra smoke flavor.

Place the marinated lamb shoulder on the indirect heat side of the grill, close the lid, and cook until the internal temperature registers 140°F on the probe thermometer, about 45 to 60 minutes.

Using tongs, transfer the lamb to the direct heat side of the grill and sear for 2-3 minutes per side until the internal temperature reaches 145°F for medium doneness.

Remove the seared lamb from the grill and let it rest for 10-15 minutes on a cutting board before slicing.

While the lamb rests, prepare the chimichurri sauce by combining all the sauce ingredients in a food processor or blender and pulsing until chopped and combined but not puréed.

Toast the slider buns, optionally with butter on top.

Thinly slice the lamb against the grain into slider-size pieces using a sharp knife. Slice off any excess fat that didn't render during cooking.

Assemble the sliders by placing the sliced lamb on the toasted buns and topping with chimichurri sauce.