I made it with the two ends right down to the concreter floor, then a base in between the two ends with the other 2 uprights on it, though will add a rail across the front and 2 more uprights hard against the end 2 to support the rail. so i suppose really that it is going through the base.
All mdf is glued and screwed and joins are strong type (top is on top of uprights so that the upright would have to fail to make the top cave in, as opposed to the top being screwed to the side of the uprights, which would be asking for trouble)