I lay the uni in the orientation that I need over a light layer of plain weave glass cloth. It could be plain weave carbon but when Uni carbon is way cheaper than plain weave carbon the uni carbon and glass combo gives best value, given the plain weave is mainly for handling.

Because I only lay the resin with a light touch to the squeegee on to of the surface of the uni it does not move around. All laid up on flat surface and then it moves together because of the plain weave. I've had no issue with fibre orientation.