First buy some cheap interlocking plastic floor material from a Home Depot kind of store (eight 12x18" sheets cost me the equivalent of around 3USD).
Join the sheets with cable ties and cut out sections for equipment.
The whole thing is kept in place by the light fitting and the pieces of plastic that protrude downwards (see first pic).

Join the sheets with cable ties and cut out sections for equipment.
The whole thing is kept in place by the light fitting and the pieces of plastic that protrude downwards (see first pic).