to get the hoverboard you have to do the following steps:
-go to desolo
-find datarecorder,it is marked with the blue symbol if you want to see it better use the compass you can acces whith holding r
-use dynamite and blow up the datarecorder
-take exo chips
-go to mat which is now also marked with the same symbol
-give mat exo chip
-give mat 2 zinc
-give mat 2 copper
-give mat 2 aluminum alloy
-give mat 2 plastic
-activate mat
now go to a landing pad or somewhere you can acces missions and stuff
you should now have many completed missions take their rewards and one reward of them should be one hoverboard and its shematic
i hope could help you get the hoverboard
and why not check out my guide how to get vtol?