Planning on building a 4 x 4 table out of cypress. I should have enough lumber in my inventory to do a top that is 1-1/2 or 1-3/4 thick. Planning on the apron for the top to be @ 5" wide with 90 degree butt joints at the corners. Two sides will have a 48" x 5" skirt the other sides will be 38" x 5" skirt with @ 11 slats running parallel to the 38" run with @ 1/4" gap between slats. This works with the lumber I have.

My question is how to join the @11 38" x 3" slats to the 48" sides of the top. I have a domino and can let them in this way. Not sure on movement since it is outdoors. Do I mill a groove in the 48" sides and put a tongue on the 11 38" x 3" slats and put spacers in the groove between the tongue and if I do this do I glue on the tongue of the slats or let them float as well as the spacers?

Open to suggestions, looking for the best way to allow as much wood movement so I don't get cupping etc...

Thanks.

Brian