The basics are 5.5" x 12" cardstock scored at 1", 2", 4", 6", 9". This gives panels of 1", 2" and 3" x 5.5". Then I cut the DSP .25" smaller for each panel.
The sentiment is stamped on a piece that is long enough to attach to the 1" panel beneath the DSP.
If you want to be able to put in in a standard A2 envelope be conscious of how high your image on the 3" panel sticks up.