The gown is made from a very thin printed muslin, bought from this seller on eBay. As you can see it has short puff sleeves, with detachable long sleeves, and a flounce at the hem. Unlike my other gowns from this period it is not lined in the bodice, since I found when studying preserved sheer gowns that most were unlined. For womeone used to making mostly early periods, this felt a bit strange, but it turned out to work just fine.
The gown opens in the back and is closed with two drawstrings. The lower edge of the bodice has darts in front and is gathered in the back. The skirt was then gathered and sewn to the bodice with a french seam, which also acts as a casing for a drawstring that that tightens the "waist". There are drawstrings also around the neck. The ones in the back start at the shoulder seam, which is placed far back, and the ones in front start roughly at the collar bones.
I need to teach Rickard about distributing gathers. Or get a lady's maid ;)
Flounces become more common around 1810, which together with the long sleeves gives the gown it's date, while the drawstring cosntruction could be (much) earlier.
The long sleeves are attached to the short ones with buttons and loops. The buttons are the same as at the wrists:
Under the gown I'm wearing a shift, regency stays and a petticoat, they can all be seen at the bottom of the page here.