Here is a card I designed this. As the name indicates you pull on each side to reveal the inside of the card. I used SB & GBS for this one. The scalloped oval is the only thing from SB and can be replaced with any shape or design you would like. I have a 2nd smaller oval on the "front" page that I used to "layer" with. It is not needed, but I like it.

Assembly Instructions 1. There are five pieces used in the sliding card. 2. We will be creating a sandwich starting with the "bottom". 3. Next you need to apply quick drying glue or adhesive runner and line up the "stop" with the "bottom". 4. Now line this "bottom" assembled piece with the top and being careful to keep them lined up, cut down the center so that all pieces are the split in half.
MAKE SURE TO REMOVE THE CENTER SHAPE, DO NOT CUT IT!!! These can be cut separately, if you wish. I found it easier to do all at once so that I got them exact. 5. Lay the "inside" piece in the center of the "bottom" piece.
DO NOT GLUE!!! It may be easier to embellish before adding this piece to the inside. Repeat for both sides. 6. Apply glue to the edges of the underneath of the "top" pieces along the top, outside and bottom.
DO NOT GLUE THE CENTER!!! 7. Add the "cutout" center shape in the opening and finish embellishing.