Whether you’re making plastic covers for appliances or other purposes, the process is basically the same. Always make a pattern before cutting your plastic vinyl. Plastic materials have little give, and straight pins leave holes in the plastic, so there's no room for error. Fabric stores sell plastic vinyl in rolls. Or, purchase an inexpensive flannel-backed plastic vinyl tablecloth.
Measure the width and length of each “side” of the item, such as a toaster's sides and top. You want as few of pattern pieces as possible. For instance, for a toaster cover, measure from the front bottom edge, up the front, over the top, and down to the back bottom edge to form one piece. Add two inches to the length measurements, the width measurements and the depth measurements for seam allowances. For example, if the toaster side measures 8-inches wide by 10-inches long, you’ll need two pattern pieces measuring 10-inches wide by 12-inches long.
Measure and draw the pattern onto tissue or newspaper according to the measurements from Step 1. A toaster cover has two sides and one front-back-top piece.
Cut-out the pattern. Arrange the pieces over your item. Pin the edges together with the wrong sides of the pieces touching. To decrease the bulk of the plastic, the sections will be encased in double-fold bias tape, thus eliminating turning the cover right-side out as you would fabric. Make any adjustments. For instance, if the toaster sides were snug, unpin, place pattern onto another piece of tissue/newspaper, and draw a new piece.
Place the pattern pieces atop the plastic. Tape. Cut out the pieces.
Assemble the cover by securing the pieces with tape.
Measure the length of the seams. Add two inches to each seam measurement. Cut bias tape for each seam to these measurements. For instance, a toaster cover requires two pieces of bias tape: one for each seam on each side of the toaster from the bottom front, over the top, and down to the bottom back edge.
Remove tape from the seam to be sewn. Insert the seam into the bias-tape fold. Because the bias tape is double folded, there are no edges to be hemmed.
Place the bias tape encasing the plastic seams under the sewing machine pressure foot. Use a medium-width zigzag stitch and ½-inch seam allowance to sew. Fold the tape ends under and sew. Use a needle intended for vinyl or the needle will break.
Continue for all cover pieces. When you have finished sewing the cover, measure along the bottom edge. Cut bias tape in that length plus two inches. Insert the bottom edge into the fold of the bias tape. Sew using a medium-width zigzag and ½-inch seam allowance.