Photocopy the photo you want to use in your decoupage using a color or black-and-white photocopier, depending on the effect you desire. You are using the photocopies rather than the original photo. Reduce or enlarge the size of your copies to fit the surface. Make certain you make high-quality photo copies for the ideal effect. Make extra copies in case you need to make repairs to your decoupage one day.
Cut out a circular or square coaster from chipboard with scissors, rounding the corners. Chipboard is a cheap form of cardboard used to make boxes or a board made from compressed wood and synthetic resin.
Apply a base coat of acrylic paint with a paint brush using a color matching the background of your photo or in a neutral color. Brush two to three layers of paint onto the coaster, allowing the paint to dry completely between each coat.
Cut out the photo from one of the photo copies you made using scissors.
Arrange your photo onto the coaster, then apply a light coating of Mod Podge over the photo to paste it, using a small, flat brush. Mod Podge --- which comes from the term "modern decoupage" --- was invented in the 1960s as a combination glue, sealer and finish and as a smooth, fast-drying sealer to protect decoupage.
Apply additional light coats of Mod Podge over the coaster and photo to seal your photo.
Allow the coaster to dry thoroughly, about one to two hours, then apply another light coat of Mod Podge over the photo and coaster. When the second coat dries completely, repeat the process of applying light layers of Mod Podge over the photo and coaster four more times, for a total of six layers. This process creates a smooth finish and a painting-like effect.