The thick trailing edge provides a large, strong area of low pressure behind the wing, and an enormous amount of drag. This low pressure causes at least two lateral vortices per wing trailing edge, one relatively small one rolling upward from the bottom, and another rolling downward from the top. The air coming from the top is moving faster, so the top vortex has more velocity, and since the density is assumed to be the same or very nearly so, it has more energy, and augments downwash somewhat. This, I believe is part of why the ugly thing can fly so slowly. All this happens on any airplane, but the effects here are multiplied because the trailing edge thickness is such a large percentage of chord. It is not efficient in terms of being able to fly fast with little horsepower, but it seems to be effective in this application, since the mission seems to be to fly very slowly. It isn't a new principle, but it is a clever and unusual application of a known principle. Effectively, it creates extra drag and converts some of that drag to lift, by adding energy to the downwash in a direction it was already inclined to go. It is not flying solely using the vortex, but rather using the lateral vortices to augment low-speed downwash and therefore lift. At high speeds, where the downwash angle is less, the thick trailing edge produces almost exclusively form drag.

Also, the low aspect ratio wing allows very high deck angles, which does angle the prop upward significantly, and splits the thrust into a horizontal and a relatively large vertical component. At the higher angles I see in the pictures, I calculate that somewhere around 5% (or more) of the thrust being generated is effectively vertical. This may not seem like much, but it has the effect of reducing the amount of lift force the wing is required to generate. And there is the prop slipstream over the center section/fuselage that helps increase lift.

It's a clever design and since it's purpose seems to be to fly exceptionally slowly; I would say by the OP's description, it has succeeded. I think it would be fun to talk to the designer about his ideas.

Incidentally, the low pressure above cannot be separated from the higher pressure below, when determining the cause of the lift force, since as Dick and others pointed out, it's the DIFFERENCE in pressure that imparts acceleration to the air, causing lift. It isn't the curvature alone of the airfoil that causes the lower pressure above, since we all know that curvature is not necessary to produce lift. The curvature does greatly increase the efficiency of the airfoil and must be considered with AOA and speed to determine lift produced.

And I could be completely wrong.