The first thing that you must do is to make sure that your hinging on you ailerons and or flaps are already done and working freely and correctly.
Now fold the flap/aileron so that the aileron/flap is just about underneath the wing and just about level. See Fig 2. below.
Make a very runny past of epoxy resin and micro balloons (Tomato Sauce consistency) and add pigment (if required) coloring to match your wing color. Poor this mix into a piggy-bag (plastic coin bag) and cut the corner off. Now squeeze the mixture on to the junction of tape and aileron/flap and continue to the full length of the wing. See Fig 3. above. The mix must be able to flow across the tape and wing skin junction, so it must not be thick.
Now get your helper to fold the wing over on the hinge while keeping the aileron/flap as close to level as possible, use an old credit card and from underneath guide the Sellotape into the cavity. You will end up with the wing in an upside down position.
See Fig 4.
Fig 5Fig 6 Carefully jig the flap/aileron with masking tape and rig it up on blankets as seen in fig 5 and let dry over night. See Fig 6.
The angle between the wing and control surface must be enough to cause the tape to form a curve into which the mixture can flow.
Once dry you can remove the tape and admire your handy work. If you have used the coloured Selotape as described above you will find that there is no glue residue and the knuckle will be nice and smooth. Requiring only a light sanding along the front edge to get it nice and straight.