Boot floor?

[S_123]

I want to screw my amp and small extinguisher case to the boot floor.
Obviously I have a spare wheel there, what can I use as a floor?
I will want to get to the spare if needs be, so I need it to be removable.
I have carpet so I will be fitting that to it too.
MDF ideal?

 

[xxxic3xxx]

yea mdf just trace the carpet and cut it out ive just done it as past of my sub install in the wheel well