Preheat grill to 300°F for even, moderate heat that cooks raw sausage without burning bread.
Mix softened butter with minced garlic, parsley, and chili flakes until uniform and aromatic.
Slice baguette lengthwise three-quarters through, hollow out interior leaving ½-inch walls.
Cut pepper jack cheese into uniform ½-inch cubes for even melting.
Remove any remaining soft bread from interior, ensuring clean cavity with intact walls.
Brush garlic butter generously on all interior surfaces and lightly on exterior crust.
Layer cheese first against buttered surface, then place raw sausage links on top. Add extra cheese if desired.
Close bread securely without foil wrapping for direct grill contact.
Place sausage-side down on grill grates. Cook 20-25 minutes until sausage browns.
Flip bread over and cook 10-15 minutes more to finish bottom and melt cheese completely.
Check sausage reaches 160°F internal temperature. Rest 3-4 minutes, then slice and serve hot.
