Many times it is hard to find someone to train with and this can be especially difficult when you need a spot or someone to hold the boards when performing a board press. One solution to this is to take a mini-band or light band and put each end in the safety pins of a power rack. At this point, lie on the bench and wedge the board between the band and your chest. This should keep the board relatively stable.

Hope this helps,
Jim Wendler