Selection/Masks/Creating a white background
Hello everyone, I consider myself to be an advanced beginner in PS. I've been using it for years, but never learned it fully. I own a bake shop and take pictures of my baked goods mostly in a photo box with a white backdrop and foil reflectors on the sides. The raw image comes out with the background looking grey (see below). I am trying to make the background a true white but no matter how close I make selections, it's never smooth. My final image isn't perfect and has softer edges VS sharper (which is what I am aiming for). I am using a laptop but considering buying a pen; is it necessary? I think I am on the right track but i just cant figure it out. If someone can help, I'd really appreciate it.
Raw JPEG Image:

After using selection tool, creating a mask, and using a paint brush (in black/white) to refine the edges the best that i can.

