That Oklahoma clay, if there's
enough and it's the right consistency, would be great to build with. With several forms made with
wood, all of equal size, you could mix the clay with enough
water to make it workable, mix in some of that grass and fill the forms. After some time in the hot sun, you'd turn the clay out of the forms to continue drying in the sun. This will essentially create adobe bricks of uniform size. When you build, you would lay the bricks as you would for a regular brick house, but use good, clean, wet clay as the mortar. Wet enough to scoop and spread with a trowel. Smooth it out on the inside and outside as you go so that it gives a nice, smooth look. When your walls are complete, let them cure a bit, then give the outside a couple of coats of a light-colored paint - this will serve to not only protect your adobe walls from hard rains, but also, the light color will help reflect sunlight to help keep it cooler inside.
Not a perfect plan, but I would give it a shot if it were me. Make a few and put them together to see how it would hold.