Foamcore are an incredible asset for work inside and outside the studio, but there is always the question of mounting them. One way is using a reflector arm and another is holding them with pony clamps, there is even a DIY holding solution.
The nice thing about this solution is that its super low footprint on one hand and completely portable on the other.
The stud on the baby plate goes on a C-stand or a grip and the baby plate is gaffed to the foamboard. between the $10 of the foam board, and the $13 of the baby plate this is quite an affordable solution if you own a C-Stand
[Baby Plate Bounce Card GEAR HACK | Tony Roslund]