Footnote number 4 in the article on Breeches and Trousers on the War of 1812 web site has this to say about linings (this was mentioned up thread but this is the full quote):
4] Standing Orders of the 33rd Regiment  make no reference to lining material for the tall gaiters but do make reference to lining material for the short gaiters. p.29
I interpreted the footnote to mean that the short gaiters were fully lined. I lined mine like so:
As you can see, I advocate for the instep strap to be fastened on both ends, just at the tongue seam. The button plaquet on gaiters runs down the side of the leg, ending up over the side of the heel. When I initially started making AWI period gaiters, I tried buttoning the instep strap to the bottom button on the plaquet. This didn't work well - the instep strap needs to pull to the rear over the heel to reach. This twists the gaiter around on the foot.
There is a good image of a pair of original long gaiters on page 43 of "A Soldier Like Way", which show that instep strap fastened at both ends at the tongue seam. Even though this is a Seven Years' War item, it shows everything we continue to expect from a British military gaiter; a tongue, a button plaquet, no front seam, and a rear seam.
The gaiter shown at the link below is also 7YW vintage. You will see that the instep strap has one free end, but it does not button to the bottom button on the plaquet, rather there are two buttons at the tongue seam.
https://janeausteninvermont.files.wordp ... museum.jpg
BTW, does anyone happen to have a full copy of the 33rd Foot Standing Orders ca. 1813?