How Do I Make this Bracket?

[Wongster]

Hi guys,

I'm currently planning to start my build of a tiny bending brake based off a plan I bought from Mogen Kilde. I'd so far gotten the 3D model done to give me some visual of how things fit and work together. Gathering of materials will start after the the lunar new year. 

While going through the processes in my head, I couldn't figure out how the brackets are to be made. This is how one looks like:

   

I don't have a slip roll in the shop.  I was thinking of milling out the inner shape in aluminium and form a 3mm steel sheet over it.  Very little experience in processing sheet metal and I have no idea how accurate the brackets need to be. 

Any suggestion and/or help is greatly appreciated. 

Regards,
Wongster