There are so many different materials you can use as a backer. A lot can depend on how stable your piece is. If it doesn't need support, then poster border type paper works really well. Felt material is something I use a lot on ornaments as it is light weight. A thin wood of course works well, and you can stain or paint it. I use E6000 to glue most of my items. It has a great hold and gives you plenty of time to adjust or align your work.