Looks like you have to connect the gas flex directly to the valve and no other other fitting in-between since the valve itself has already the flare male and the hose is flare female, you can't put either of those fittings because they're taperd and not flare the question is only if the valve and hose are the same size if not then you need a flare reducer or another size hose, and no sealant should be applied on treads of a flare connection since the seal is achieved by the flare being tight and not through the treads.