(Optional) I always take my sub buns and hollow them out. The excessive bread isn't necessary for me, so after I slice 'em in half, I'll take a spoon and scoop out some bread from the crown.
Heat the Blackstone at Medium-High.
Slice the P&O (peppers and onion) thin, and ready it for the Blackstone
For the sandwich, I recommend taking the sausage link and halving it. You'll use both halves for the sandwich, but you'll get the right amount of char.
Throw the peppers/onion on the Blackstone and heat 'em up until soft and cooked.
Keep the P&O heated and add the sausage until cooked & charred.
(Didn't for this, but recommended) Add the sliced provolone to the P&O until melted. Good time to toast the sub buns on the blackstone as you ready to combine the ingredients.
Remove the bun, add one half link to the bottom. Scoop the P&O onto the bun and top with the other half of sausage.
Drizzle (heated) marinara sauce atop the sausage/P&O and top it with the other half. Press the bun together to make that sandwich look beautiful
Eat it hot, it's a delight!