Sand all surfaces of the tray and balls with 100- and then 150-grit sandpaper. Remove the sanding dust with a tack cloth.
Mix equal amounts of bright green and white paint. Use the flat brush to base-coat all surfaces of the tray with this mixture.
Paint the inside flat area of the tray red. Apply additional coats as needed for complete coverage.
Paint the balls bright green.
Lightly sand the sides of the tray with a paper grocery sack to remove the wood grain the paint raised. Remove the sanding dust with a tack cloth.
Using the rubber stamp and black ink pad, stamp the image onto tracing paper. Use graphite paper to transfer the stamped design onto the front and back sides of the tray as many times as needed.
Use the brushes and paints to paint your design as desired. (We used the round brush and green, red, blue, and yellow to paint the ornaments. We mixed green with a small amount of white and used the liner brush to paint the greenery.) Let the paint dry.
Use the fine-tip black marker to make outlines and add details.
Glue a wooden ball to each corner on the bottom of the tray; let the glue dry.
Apply two coats of matte-finish varnish, letting the varnish dry after each coat.