My suggestions are in light of boneless on the 3 burner silver.
I would put it on a rack, in a roasting pan or a quarter sheet pan. Season the roast heavy with salt and pepper.
Remove one grate and center it so there is room to place a smoke tube on the right side direct on the Flav bars.
Preheat the grill all burners on high for 15 mins or 450 500F lid temp. After preheat set burners, Low off off front to back.
Put the roast in, in the rack and move it to the back. Add a lit smoke tube.
After 30 mins turn the sheet 180 degrees to even the cook. The front and the left side are likely a bit hotter.
Cook until 125F internal. Pull, cover with foil while the grill preheats, crank all burners on high, add the other grate. Heat to 400++ sear direct, 60 to 120 seconds a side.
Two or three or four flips per side.
Pull, rest, carve, enjoy