I had 19 sessions so far on the foil, the last 11 with the shown DIY front foot hook.
Found this aluminum bar in a hardware store : 40cm long, 3.5cm wide, 3mm thick, with several holes in it already.
Strong enough not to break but it still has flexibility. I rounded the edges to prevent injury from these. I modified it a little bit so the screw heads do not stick up over the aluminum surface when mounted.
I bent it like shown at three points which should make a good result for most foot heights. The upper part is 18cm long.
The holes were already in it and they were eventually at the right place to fit the holes of the strap inserts of the board. This way mounting was very easy and the foot hook can be mounted more fore or aft.
A foot strap or similar can be put over the upper part and secured with a plastic covered thread through the hole in front. I usually ride with shoes and had no problems with any injury by sharp edges from the foot hook this way. On the soft pad the mounted bar sinks somewhat into it and is quite even level with the pad surface. Riding barefoot? You might need more rounding of edges...
After some crashes the hook had been bent up but it was very easy to bend it back, even on the water in choppy and gusty conditions.
What I would change: I would shorten the upper part of the bar to about 10cm. The reason I left it at 18cm so far was because this way the used foot strap covered all the metal. I didn`t have the possibility to shorten it on the holiday.
For me this DIY foot hook worked very well. Very easy to release from the board in critical situations.
On the water you can put the front foot a little aft and simulate strapless riding. Also the strapless water start can be simulated the same way.
Just my 02 cents.
Similar use at own risk.
Have fun and ride safe.