Most of these boxes are fibreglass moulded to the body at the rear of the box. The only problem with making one all out of MDF, including the rear is that you will most likely have to box out and around a few objects which will cost you internal litres. This only means that the box may have to sit out a bit further than the fibreglassed rear one would.
If you start looking up DIY boot installs for the mk4 you are bound to find someone that has made one all out of MDF. If you do, see if you can find some pictures of how they have constructed the box and post them up.
I am a cabinet maker by trade so i can do it, but the problem is making it to the correct dimensions and making it fit without having the car to work with and not knowing what is behind the box to start with.
White Scirocco R
White MK3 Golf 2dr
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