No pattern, I used Cupcake’s old dress as a template, improvising longer (3/4-length) sleeves. The underdress took 4 yards of 100% cotton gauze, dyed royal purple by the hubs. The color required a whole bottle of Rit dye in purple, plus about half a bottle of the navy blue.
The dress itself has no shaping and the sleeves are raglan, with no neck facing, so it was a cinch to sew. I made a drawstring casing around the neck out of 1/2-inch double-fold bias tape in light purple. The drawstring will be satin ribbon also in light purple.