The Snail Mail Suite is on pages 54-55 in the 2020-2021 Mini Stampin' Up! catalog. The Designer Series Paper (DSP) uses bright, fun colors and makes for quick, easy cards if you have the coordinating colors of card stock.
You might be aware of my love for using One Sheet Wonders. (By that I just mean cutting up card stock or DSP into specific sizes.) For this first card used a piece of DSP that was 3" x 3" and cut it on the diagonal from point to point. I layered this on a standard layer of 4" x 5-1/4". I did fussy cut a snail from another piece of DSP. Another piece of DSP was adhered to the envelope flap so it coordinates with my card.