This is a very vague question but here are some ideas.

1.Laminate the apron out of multiple strips of 1/8-1/4 strips of
hardwood, depending on the arc diameter.
- Create a form out of a stack of 3/4" MDF pieces cut to the inside
radius
- Cut notches in the back half of the form about every 5-10 degrees
so you can use clamps or just radius the back of the forms concentric
to the front.
- Make a sandwich of the strips, flat on a table, with glue
in-between each (use poly or resin glue that hardens to hold the shape,
not typical wood glue.
- Place the snadwiched stack against the form with clamp at the
center. Add clamps out toward each end slowly pulling the sandwich into
the form.
- Oh yeah, wax the form first or use wax paper.
- You could do this with all cheap wood and only have the outer
layer be nice or even veneer it after.

2. Do basicially the same thing but use wiggle-wood (a bendy plywood)
and veneer or outer strip.

3. Go to tablelegs.com and buy a pre-made radiused apron.

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