Clean surface, use small ball peen hammer to ding bolts down, sub-flush. NO SEALERS! Period. They act as a lubricant and allow the gasket to squish and slide, not to mention the excess can be sucked into the valve body...
Torque not as important as watching the gasket while tightening. As soon as you see the gasket beginning to squish out near the bolt, stop. Any further will tear the gasket.