Wedge tee height.

Flush. All wedges play off the deck.

The short answer

Flush with the mat surface. No tee, on any wedge.

Why a wedge and a tee do not belong together

A wedge generates spin through ball-first contact with a descending strike, where the grooves grab the cover and the ground is struck after the ball, not before it. Everything about that sequence depends on the ball sitting on the surface. Put it on a tee and you interrupt the one mechanism the club exists to produce. The ball comes off higher, with less spin, and it will not check when it lands.

You will also never face this shot. There is no situation on a golf course where you tee a wedge up, so there is no version of this that counts as practice.

The practice exception, and its limit

If you are specifically working on knockdown or flighted wedges, some players like a fraction of air under the ball to rehearse the feeling of a cleaner strike. A quarter inch is the absolute ceiling and it should be the exception, not the setup you leave in place. Anything more and you are training a sweep.

The mat problem is worse with wedges

Wedges have the most bounce of any club in the bag, and bounce is designed to interact with turf. A hitting mat does not behave like turf. The rubber underlayer resists the sole rather than yielding to it, so the bounce that would have glided through grass instead kicks the club into the back of the ball. A thin, bladed strike and a slightly fat strike can produce nearly identical results on a mat, which is why wedge practice indoors transfers so poorly if you are only reading the numbers.

What to watch instead of the number

For wedges, strike location tells you more than carry distance does. Foot spray or a marker on the face will show you where you are contacting the ball, and the mark you leave on the mat will show you where the sole arrived. Both of those are honest. A carry number off a mat, with a wedge, is the least reliable figure in indoor golf.