We made this quarter sheet card and envelope at my workshop last week. The card is a quarter-sheet of cardstock, so the card size is 2 3/4 X 4 1/4. I got this idea plus the measurements for the envelope from the amazing Jackie Topa. On her blog, Addicted to Stamping, she has a sheet you can download that has the measurements to make many sizes of envelopes using the Simply Scored diagonal insert.
All 3 patterns of DSP are from Paisley Petals. We sponged the bird with Marina Mist ink to make him stand out a bit more. The sentiment is from You're My Type.
The envelope is made from a 6X6 square of DSP, so you can make 4 cards and matching envelopes from 1 sheet of cardstock and 1 sheet of DSP!