In article .com,
"Jim" says...
Hi and thanks for replying.

I want the bracket to arch across the span. I would also ideally like
the cross section of the arch to be rectangular with rounded edges
(I'm envisaging the cross-section of the arch being about 2" wide by 3"
high).

Currently the only tools I have are a basic workbench, a jigsaw (I
think I could use this to cut the arch shape), electric sander and a
Makita 14.4v drill.

I don't mind buying extra tools since I plan to do more diy in the
future. However, I'm not sure which tools you mentioned would be most
useful for this job. Could you please suggest what would be most useful
for me to buy?

A drum sander attachment for the drill might be useful for smoothing
and rounding if you don't fancy getting a router. A set of wood
chisels (and a mallet) is pretty much essential.