Use the paper that copy papers reams are packed in. I get it free from local copy shop.

Generally speaking, it is recommended to remove the freezer paper from finished quilt projects. While it may not matter in a wall quilt design that may never be washed or handled, the paper could crumple or shift inside its appliqué shape, and may affect the quilt's appearance and feel. Personally, I would also feel concerned about the paper's acidity causing yellowing of the fabric down the road. I hope that helps!

Is it advised or necessary to remove the paper when using freezer paper to apply appliques?

I use a lot of freezer paper when I do applique', but didn't know there were so many more ways to use it. Especially like the label idea