Test the wash on paper or on the back of the slate. Allow some of the slate's border to remain unpainted to enhance the rustic character of the piece, or add a speckling of light-blue paint at the edges with the sea sponge. Allow the piece to dry. Tape the stencil in place on the slate. After removing the skin from the oil sticks, apply the colors to your palette.
Oil sticks are very creamy and blend nicely.
Apply the lightest colors first, then the darker ones. Rearrange the stencil as desired to cover the piece. When you're finished, allow the slate to dry. When the slate is dry, spray it with two coats of acrylic sealer, allowing it to dry between coats. If the piece is to be used outdoors, apply additional coats of spray, and repeat monthly.