First make sure your the cue ball will bounce predictably off of your tray. Some trays have an edge that stick out and the cue ball doesn't bounce well off of it. Also make sure the side you're using isn't cracked. Place the tray, filled with all of the other balls against the long rail with one edge at the first diamond. Put one of the object balls on a piece of chalk along the end rail, making sure that none of the ball is hanging over the edge of the rail. The exact position can be adjusted, but in the video, I have it about 1 1/2 diamonds from the corner pocket. This is about as far as it will roll. You can set multiple ones up to dress it up a little.

I start with the cue ball two diamonds away from the end rail and one diamond out from the side. Find an aim point on the far rail and keep your hit constant. Either adjust the aim point so the cue ball hits the object ball correctly, or adjust the chalk and object ball into the cue balls path, making sure it'll still get to the pocket.