Adding a bit more water may help it stick together better...or maybe it's missing something else that could help with that. If I ever figure it out, I'll post it here...but until then, this is a great substitute!
Just remember that it falls apart VERY easily, so I usually end up rolling it out but then cutting it up and piecing it back together in the pan.
WEMP Free Pie Crust
1 1/4 cups wheat-free flour mixture
1/2 tsp xanthum gum
3/4 tsp salt
1/2 cup shortening
4 Tbsp cold water
1. Combine flour and salt in a medium bowl; cut in shortening with a pastry blender until crumbly. For a flaky crust, the crumbly mixture needs to have irregular-size pieces of shortening as small as dried peas and as large as English peas.
2. Sprinkle cold water, 1 Tbsp at a time, evenly over surface; stir with a fork until dry ingredients are moistened. Cold water is important; add ice to water before measuring. Add 3 Tbsp water, tossing mixture gently with a fork. To make sure you've added enough water, squeeze the dough between your fingers. If it falls apart, gradually add the remaining 1 Tbsp water (don't over stir because it will toughen dough)
As you stir with your fork, watch for it to look like this. You'll know it's ready to stop stirring and to squeeze dough together to form your disk:
3. Shape dough into a flattened disk; wrap in plastic wrap, and chill 2 hours or freeze 30 minutes. Chilling dough gives the flour time to absorb the water.
4. Roll dough out to 1/8 inch thickness on a floured surface.
Before rolling the dough let it stand at room temperature for 5 minutes to help soften the fat. Using a cloth-covered rolling pin minimizes the amount of flour needed during rolling. Roll dough from the center out to the edges into a 12-inch circle.
5. Place in a 9-inch pie plate; trim off excess pastry along edges. Fold edges under, and crimp.
to transfer pastry to a pie plate, fold dough in half; place in center of pie plate, and unfold. or loosely roll the dough around the rolling pin; then starting at one side of the pie plate, unroll the dough over it. press dough gently, without stretching into the bottom and sides of the pie plate using your fingertips (stretching the dough causes it to shrink during baking) if the pastry tears, dampen the dough, and press on a scrap of rolled-out dough to repair the break.
Trim pastry so that it overhangs the pie plate rim by about 1 inch. Fold edge under to form a ridge; pinch the inner rim of the dough with the thumb and forefinger of one hand while pushing against the outer rim of the dough with the forefinger of the other hand. (to keep from poking holes in the pastry, bend your fingers and press with the knuckles) to help prevent shrinking, use one of these methods: lightly press the outer points of the pastry under the rim of the pie plate; or freeze until rock hard and bake without thawing.
6. Prick bottom and sides of pastry shell generously with a fork for a baked pastry shell (do not prick if the pastry shell is to be filled before baking).
Pricking the bottom and sides keeps the pastry from puffing or bubbling during baking. If it does begin to puff, reprick the crust. (omit this step for pastry that bakes with a filling.)
7. If baking before filling, bake at 450 for 10 to 12 minutes or until golden brown. Cool on a wire rack.