Glue or baste (use regular sewing thread) the stitching and backing to the matting board. If you are using a square be sure to carefully mitre the corners. If you use a circle or heart shape, carefully fold (or carefully cut if necessary) small darts in the linen and shape it around the board as you glue. If you decide to glue the piece, allow the glue to dry well before going on to sew the pinkeep. If you baste, it will not be seen once the pinkeep is sewn so the size of stitches and color of thread is not important. See the above photos for a mitre corner and basting the piece. While basting you are stitching very slightly and carefully into the batting. The fabric or linen should be taut on the front side of the board. You can pin into the sides of the matting board as done with lacing if you need to in order to hold the linen or fabric taut. Remove the pins after the piece is basted.