All the places for holes and cut lines marked. I used a small screw driver and a hammer to make some markings for the drill bit.
No fancy drill press here so I had to use a regular cordless drill. Aluminum is quite soft metal so drilling was easy.
Yes, it is not hard to make holes to aluminum freehanded but getting the hole where you wanted it is totally another thing. My aim is not to make a showpiece out of these clamps so this is something that I accepted from the start.
Your wife/girlfriend will love you for all the metal shavings that will attach themselves to socks, shirts etc. :)