With my jaw at rest, not mewing, the edges of my tounge rest between my teeth and jaw is jutted forward.
Because I have a high arch and small intermolar, to mew I basically have to suck my tongue up to the top in the middle and then drops down on sides to push the sides of teeth and gums, but then it hurts and I get a scalloped tounge.
I can get the tip and back okay, it's the middle that's difficult...