I have now been foilboarding since 2005 and have taught a few friends how to do so over the years. Thought I would share my experience and hopefully also learn from others as my technique is the complete opposite of what I hear is done in kite schools these days.
Trend is as I understand that you should start with a high volume board with a short mast and high area low aspect wing ? You then work your way up to longer and longer mast? I believe that is the way most schools organize their foilboarding lessons?
I have tried this technique a couple of years ago and returned to my original way of teaching as the success rate was much higher and progression much easier.
Instead of using big high lift wings, I use a wing which is very small, less than 500cm2 in combination with a very short mast (45cm). The problem with very big wings is that they engage almost immediately after the waterstart often resulting in a immediate wipe-out for the student. They have no choice , either fly or fall. With a small wing they are able to waterstart and ride the board on the surface up to a certain speed (typically just above the boards planning speed) without lift off . This means they are able to ride almost normally back and forth and get the feel of the foil in the water as long as they stay bellow that critical take off speed. Experienced kitesurfers have no problem doing that! In every case they are able to ride a “foilboard” right from the start, stay upwind easier than with a surfboard (even if they are not flying), never have to walk upwind carrying the board.
When they are ready (their call), a little extra speed will engage the foil and get them flying touch and go but with easier balance than on a slow flying wing as they are moving faster. At this stage having a short mast and flat water really helps as it reduces the chances and pain of wipe-outs compared to a long mast.
Next step is using a bigger wing (up to 800cm2 max) and progressively increasing the mast length. Super big wings (above 800cm2) are not necessary when using this method unless you are super super heavy.
About the board I found that big (around 150cmx50cm) low to no volume boards like the ones they now make using TT construction were the easiest to learn on. Boards with high volume are more difficult to waterstart as they are harder to put on the rail and keep onto the rail+ you waterstart lower into the water.
Kite size used when learning is close to the size they would be using on a surfboard .