On the Subject of Mat Boards….
Most of the stores listed in Part 1: Purchasing sell frames with pre-cut mats inside. If I don’t want to use those mats for the art I am framing, I will put them aside for matting prints, or other future artworks. If it is a single-layer mat, I can generally cut it larger if I want. (I have my own mat-cutting tools at home.)
Purchasing Mat Boards….
Art and Craft supply stores (Such as Michael’s, Hobby Lobby and Jerry’s Artarama) will sell mat boards, pre-cut and the uncut large size of 30x40”. The prices at these places are in my opinion not worth it unless you have a coupon (my goal is framing on a budget, remember). If your area has a “discount art supply store”, check there for the uncut mat board. I live in Houston, and we have a place called Texas Art Supply. Their uncut mat boards are 40%-50% cheaper than Michael’s, Hobby Lobby and Jerry’s Artarama. Granted, it is a “discount art supply store”, so they never have coupons or sales, because the prices are already discounted, every day. If you’re out of the area, you can order from them online. (Not sure if that includes mat boards, but all of their supplies are discounted.)
If you cut your own mats, always save the leftovers. I usually cut mats for 16x22”, 9x12”, 11x14” & 13x17” art, so can get at least 3 cuts out of each uncut board.