The same principle can be applied to most foam wings. Here I have cut the ailerons at a reverse angle but I am sure the same principles will work if cut at the more conventional angle.

You will need the following tools:
Razor saw, Masking tape, PVC tape or Sellotape, Bathroom silicon.

1. Cut the aileron out using the razor saw at an angle shown..

2. Looking from the end of the wing section. The aileron is cut from the wing at an angle (marked in red). Then hot knife a groove down the wing as marked in blue. When hinged the aileron will the tuck neatly into the wing when it is deflected.

3. Turn the wing over and align the hinge and tape the aileron in place. (I used "Diamond" sellotape)
Make sure that the top surface of the wing is level and also make sure the tape is well adhered to the top surface, otherwise you will get flashed silicon onto the top surface.

4. Turn the wing back over and mask off any areas where you don't want silicon. (It might get messy!)

5. Apply a silicon bead of approx. 1.5 mm in width. (no more than this)

6. Run your finger down the bead smoothing it out and removing any excess.

7. Now close up the hinge fully. This will do two things 1. "Wet" both surfaces. 2. create another small bead of silicon along the hinge. Carefully open out the hinge again and run your finger back along the new bead. Again removing any excess. You may need to repeat this step until you hardly get a new bead forming.

8. Set the hinge in position and leave overnight. Wherever you set the hinge this is where it will naturally settle. Some people prefer to cure the hinge open, therefore leaving a bit of tension in the final assembly.
Personally I prefer a hinge which settles in the neutral position.

Finally remove the tape and the masking tape, leaving you with a perfect hinge.

Additional notes: I was surprised by how little silicon is required for a strong hinge.
If you do not remove the excess silicon as described in step 7 you will be left too much silicon forming a filled joint rather than good hinge.

It is also a good idea if you have the scrap foam that the original wing was cut from use this to hold the wing in position while you are working and more importantly when the silicon is curing. I also weighted the foam down so the hinge was aligned perfectly neutral and with the top surface.

Don't be worried if you do stuff up or you don't get a perfect hinge the first time. Simply fold back the hinge and then run your thumb down the silicon and it will easily peel off so you can start again.

This hinge not only looks great but is actually really strong. I had accident which wrote off the wing yet the hinges were fine!