Use an exact-o knife to cut your foam core board to 14x16 inches. Place the board in the center of the piece of felt or burlap that is 18x20 inches. (You will be glueing the candy to this fabric, so see photos to decide whether you like the candy contrasted with red or burlap better.)
Use a stapler to wrap the edges of the fabric around the back of the board. You can trim the excess fabric if there is too much to staple easily.
Use the same method described above to staple the 20x22 inch piece of burlap (or felt; whatever is opposite of what you just did) to the plywood.
Use the stapler to secure the smaller rectangle (foam core board) onto the covered plywood. Think this through before you staple; you should only staple on spots where you KNOW you want to glue candy so that the staples aren't visible.
To get the oval shape around the tree: get a large piece of paper and cut it to 13x15 inches. Fold the paper in half horizontally, then vertically (into quarters; look at the folds you can see on the picture). Then use a pencil to draw a curve on one edge (the edge that doesn't have the fold.) Use scissors to cut the edge. Unfold it. It should be an oval shape that is about a half inch from the edge of the felt (or burlap) covered foam core board on each side. Use a pen to trace the oval (you will cover up the marks with candy anyway.)
Start by glueing candy on the oval before you start on the tree, to make sure you have room for it.
Use lots of glue and candy to make your tree. Don't forget to embellish the corners.
Once your candy is all glued on, let it dry at least overnight.
Nail or screw in a picture hanger on the back.
To store: Use two large pieces of cardboard that are the same size (larger than the wood). Use pieces of styrofoam and glue them around the edge of one piece of cardboard. (Styrofoam must be taller than how far the candy sticks up from the felt) The candy tree goes in the middle, then the other piece of cardboard is taped on top. When you open it the next year, slit the tape on 3 sides so that it opens up like a book.
You will want to store this in your house, not in the garage or attic. The candy needs to be stored somewhere where there is climate control; if it gets too hot the candy may melt. This year I think I will take an extra step and wrap the cardboard in plastic (we have the kind of plastic that movers use to protect furniture, but saran wrap would probably work the same, you would just need a lot. If you have a sealed plastic bin that it can fit in, even better.