After some measures I traced the first lines for the support of the motherboard:

in this photo I did a test to see how much space to leave on the panel to fold it:

Taken all the appropriate measures I started to cut the panel:

The raw panel cut:

I begin to draw the lines of the left edge (some are oblique to 60 degrees):

I start to cut them…

The panel cut:

Then I polished the edges:

I mark the position of the holes for the motherboard (both atx and microatx)

The position of all the holes:

I begin to drill the holes:

Done: