Back in my kit making days, the method for making a fabric
grille was to staple some velcro on the cabinet, then
stretch the fabric over the grilled frame by spray gluing
one side, the opposite side,a third , a foe\urth and finally
pull tight at the edges.

but I'd like to get the discussion started at making the frame
for scratch build. I have failed at trying to cut quarter
round stock in a 2 cent mitre box. Nothing is square and
_besides that the sides don't line up worth squat either.

There are hand miter box systems with the saw which I've
seen, but don't kniow what level of improvement would be
provided over the old wood one. The saw looks nice and the
blade is like a hack saw blade only wider and should cut
square.

I thought of using a length of picture framing material.

Then there's the 'chord system' where the fabric is
pressed into a groove and the rope chord is forced in to
keep it in place.

I would use silk fabric because it is sound neutral.

Fastening the frame to the cabinet is usually done
with those ball and socket thingies, magnets, or the ol' velcro.
With the last kits I built, the ball and socket thingies sucked
and the pre-drilled holes to line everything up sucked too.

What methods are being used here that give an at least
bearable and at best professional look?

BTW... new info in the Group build Plug and Play speakers too.