Another way if you have a decent set of drill bits and a reversible drill..
good dose of plus gas.. leave for 24 hours..
find the center.. drill a pilot hole .. use progressively bigger drills , Don't go all the way through.. about half way..
when you are up to about 75% of the bolt diameter ..every now and then give the drill a shot in reverse ..angle the drill a tad to make it seize..
the drilling friction heat combined with reverse, anti clockwise turning will spin it out.
There are even reverse.. left hand.. drill bits for this purpose.. but I find a normal clockwise drill bit usually works..
As you say..If it's clear at the back.. just clockwise drilling may work..
I use easy out extractors as a last resort.. if it snaps off.. you're buggered.
try not to smack it too much with a chisel or center pop.. it can distort the bolt and make it tighter..
I'd be looking to see what caused it in the first place.. torque wrench good ?? do you have spacers fitted??
you tube says video not available .. strange .. anyway just google "left hand drill bit".. it's on there..