Gather stone, cobblestone, wood, glass, doors, torches, and slabs
Choose a flat location
Mark the castle footprint with blocks
Build thick outer walls
Add corner towers
Leave space for a gate entrance
Build a main gate with doors or a portcullis-style opening
Add battlements along the top of the walls
Build a keep or central tower inside
Add floors and stairs inside the keep
Place windows throughout the castle
Build a courtyard inside the walls
Add a throne room, storage room, and bedroom
Add a bridge or moat around the castle
Light the area with torches or lanterns
Decorate with banners, flags, and armor stands