I used this Video to make a mini scrap book from the envelope card. Christina Griffiths gives very good instructions here in this video.
10" x 4" and scored at 5" you need two pieces then attach them at the right side of one and the left side of the other making a middle section that will sit in the card base. You then need to cut
two more pieces that measure 8 1/2 x 5 and they are scored at 4" and 8" this leaves a 1/2" section that you can add one to another and also a 1/2 " section on the other that will tuck behind the other layout on the base of the card then folds up accordion style to tuck away in the Envelope card base.