Hoegh Osaka temporarily re-floated itself before being safely moved for further assessment: http://www.theguardian.com/uk-news/2015/jan/08/car-carrier-beached-solent-sandbank-refloats-itself

Hi Trygve,, the minimum height of blocks in the drydock ( keel & side blocks on which the ship is placed/laid) is 1,2 mtrs to allow access to works (paintworks, steelworks) on the ship's flat bottom while the ship is in drydock.
However, it is recommended the height of blocks to be 1,5 – 1,8 mtrs, and eventually a greater height of blocks which is even more appreciated by all the persons who are accessing the flat bottom of the ship's hull from the drydock floor ( Yard's workers, Owner's superintendents, Class surveyors, Paint representatives, .......) :-)

Yes, in some ways it must be quite easier with flat bottom of she ships when docking. But when working or painting on the very flat bottom, there must be arrangements to give space between ships bottom and the dock "floor"(?). I think experts can give good answers.

On this photo can well be seen, on the flat bottom of the ship, the previous arrangement of dockyard's keel & side blocks (the blocks onto which the ship is placed/laid during the drydocking time in the drydock).