What is the best way to fill the gap between the wall and floor in a room?

The best way to fill the gap between the wall and floor in a room is to use a flexible sealant or caulk that matches the color of the wall or floor. Apply the sealant along the gap using a caulking gun, ensuring a smooth and even finish. This will help prevent dust, debris, and pests from entering the room while also providing a clean and finished look.