Step 3: Prepare the handle
Cut everything into the right size, and look out for some big wood bolts.
Drill holes in the sides of the handle and use a hammer to smash the quartered end of the bolts into the aluminium.
I didn't want to spend lots of time, so I filled the steel tube with chemical anchor and put the two prepared pieces into place.
Ten minutes later: some sanding and the only thing I had to do was to drill some holes in the downside of the handle to attach it to the box.
Final phase: paint it.