First you will need a piece of cardstock measuring 10.5" x 3.75". Follow the pattern below to make your cuts and your folds:
Once everything is cut and folded, glue the cardstock piece to the inside of your card base and pop out the portion that you cut and folded. Make sure you don't add adhesive to the center pop-up portion of your cardstock piece.
Now you will glue the elements of your card that you want to pop out, in my case it was the flurry of butterflies. I myself think that covering the whole popped out piece and even overlapping it with elements that hang over the edges looks better for the eye. I didn't want any white showing at all so when I glued my butterflies in place, I glued them so they over-hung on each side and top.
When gluing the butterflies at the very bottom, I had to turn some upside-down and side-ways to fill in the flat scored area. You wan't tell because I layered some right on top of the upside-down ones to cover them: