I'm getting ready to start the dash on my car and was wondering what was the best way of fastening the dash on ?
I'm planning on using marine ply and covering it with camping mat an vinyl so am looking for fastening that don't show ... any suggestions ?

Counter sink your fixings into the wood, fill over them and then cover. Bolt from the rear. Mind you you'll have to have thick ply. I used 9mm mdf and covered with grey alcantara. ( if thats how you spell it?)

I was thinking 6mm but with a double thickness along the bottom edge, and bringing it down to the transmission tunnel an fastening there too for extra rigidity. I've seen lots of comments about using camping mat to soften it and (hopefully) provide an SVA compliant bottom edge so I was aiming to do that.

I used countersunk bolts in countersunk holes in the ply. I ground the edges of the bolt head a little to turn it from a circle into a bar then epoxied them in place into the ply dash board. I then used wing-nuts to attach onto the bolts to hold the dash in place.

I did it as per Ben but I also put a thin nut on each bolt behind the dash to make sure each fixing stayed in place.