Vests normally have facings on the collar, lapels, arm holes and bottom-edge hems. You sew a lined vest as if you were sewing two vests together. You don't need a hem, and depending on the fabric used as a lining, you can wear the reverse side out as well. Other vests may have a silk or even a fur lining. Western wear vests may be made with a flannel or quilted lining. Which fabric to use for the lining is entirely the wearer's choice.
Cut two sets of the vest following your pattern and using two different materials. For example, use a cotton or flannel lining on a denim vest.
Sew the side and shoulder seams of each vest separately.
Place the two vests together with the wrong sides of the fabric facing out on both vests.
Sew a seam around the entire parameter of the vests. Sew the front lapels, go across the neckline and down the right lapel. Sew the seam at the bottom of the right and left front pieces.
Turn the vest so the right sides of the fabric are facing out. Turn in a 1/4-inch hem around the edges of both armholes. Match the two edges of the armholes together and top stitch around the armhole. Make sure the edges are even.
Sew a row of top stitches around the outside edges of the vest 1/4-inch from the edge. Press in the 1/4- inch hem on the bottom back pieces and topstitch the edges so they match the rest of the vest.
Add buttons, snaps or other closures as desired.