My latest 3D printer, UMMD, uses a kinematic mount, often used to mount lenses and beam splitters on optical tables, to mount and level the bed.  The mount constrains motion in 6 DOF, yet allows the bed to expand when heated without creating any lateral forces that cause either the bed or support structure to flex.  It has proven so stable that after initial leveling, it has not needed releveling even after transporting the machine on its back in my car.

The kinematic mount uses three leveling screws, two with spherical heads.  One of the spherical head screws, the reference, sits in a chamfered hole that allows the bed to tilt but prevents lateral motion.  

The other spherical head screw, used to adjust the bed's pitch in the X axis, sits in a chamfered slot that allows the bed to tilt for leveling and to expand when heated but prevents rotation around the reference screw.  

The third screw, the roll adjuster, is simply a flat screw that touches the underside of the bed and allows it to tilt for leveling and to slide to accommodate thermal expansion .

The 300x300x8mm MIC6 tooling plate bed is held down onto the leveling screws with springs.  Nothing stands above the bed's PEI print surface, which minimizes the danger of the extruder nozzle crashing into clips or screws.

Details of the design can be found here.