Separate the white and yolk of an egg by breaking the shell half open and gently dropping the yolk back and forth; the yolk must stay whole and not break during the process.
Put the yolk, salt and crushed garlic inside a small bowl
Add, as outlined above, very small drops of olive oil into the bowl and stir gently with a whisk; there is no need for an electric mixer or whisking particularly fast, just enough for ingredients to blend
About one minute later, add a few more drops, again in very small amounts, whisk between oil increments. Keep adding oil in tiny amounts for the first 10 minutes until you have a thick base.
The aioli, once 10cl of oil have been poured, becomes more solid and harder to stir. It may also get caught inside the whisk, which is fine. Carefully tap the whisk handle onto the bowl (holding the latter, naturally) and repeat occasionally to retain homogeneity of the sauce. You can add oil a little faster now, at about a 2cl rate.
At the very end, add lemon juice to your taste. This will help smothen the sauce and give it a crisper, fresher color.