I have a 4m wide, 60cm deep floating desk.
Recessed into three walls.
I used sold oak slat kitchen worktop.
I did not want any legs so I could move chair to any point along its length.
I screwed 25mm x 38mm wood on all three walls to drop desk onto. I used this dimension so I could screw into wall and up into desk.
Wickes Treated Sawn Timber - 25 x 38 x 2400mm
www.
wickes.co.uk
I then put three of these, one every 1m along back wall. Note that you need notches in above wood.
• Mild steel shelf bracket with a grey finish
www.toolstation.com
To stop sag, I was going to put a 4m length of 25mm angle iron, acrewed every 40cm onto the underside (stepped in by say 15cm). But in the end i did not need it.
I finished it off with a few cable holes big enough to take plugs, filled with the plastic slots, and a cable tray suspended underneath along the back. (The cable tray was a lot more expensive than I expected).
I can happily stand on it.
Sorry I have no photos.
Sfk