Tape a plaster stencil to the wall with blue painter's tape.
Spread joint compound across the surface of the stencil with a trowel, as if you were frosting a cake. The compound should fill all the stencil openings that form the design. Remove excess compound from the trowel.
Scrape the surface of the stencil with the clean trowel to make the joint compound motif level with the face of the stencil and to remove excess compound from the stencil's surface. Continue to scrape until the stenciled areas are flush with the stencil's surface.
Carefully peel the stencil from the wall, taking care not to disturb the design.
Smooth torn edges of the wet design with a toothpick. Smooth unappealing surface irregularities with a dampened finger.
Wash the stencil, then dry it completely by gently pressing it into a dry towel. Return it to the wall to create the next design. Repeat this process until you’re finished stenciling.
Let the joint compound dry for at least 24 hours before you paint it or apply another finish.