Put a good amount of glue on the mortise and tenon after checking the dry-fit.

Assemble the parts with the best side of the skirt out.

Clamp the entire leg/skirt assembly with bar-clamps and let it dry for at least 24 hours. Be sure to check that the parts are in square with each other before the glue has a chance to set. All of the parts should have a clean, tight fit as shown.