Spread 1/2 tablespoon butter onto one side of a slice of bread and sprinkle with a small pinch each of oregano and garlic powder. Flip the bread, butter side-down on a clean cutting board, then top with 1/4 each of ham, artichokes, olives, pepperoncini. pepperoni and top with mozzarella.
Spread another ½ tablespoon butter onto a second slice of bread and sprinkle with oregano and garlic powder. Place bread butter-side up on top of sandwich. Repeat to make 4 sandwiches.
Heat a large skillet over medium heat. Place 1 to 2 sandwiches in skillet and cook until the bottom slice of bread is golden and the cheese is starting to melt, about 4 minutes. Carefully flip sandwich and cook until golden underneath, about 4 minutes more. Repeat with remaining sandwiches. Serve immediately.