The floorboards are made up of the centre which will be fixed, and the two sides, which which are removeable.
The battens which join the four slats on each side extend under the centre peice to fix them down.
A small batten at each end locates the side forward and aft. And some angled blocks (yet to be added) will locate the floorboards to prevent them sliding side to side.
They are sanded screwed together above, I have to take them apart and add a drop of glue, and then oil them when they are dry.
I'll have either turn buttons, or simple cords to hold the floorboards down on the outsides.