Use a high mixing bowl and a stick blender to mix the aquafaba, the mustard and the lemon juice. Add a bit of salt and pepper. Put your stickblender in and mix briefly. Now add the olive oil in a thin stream until the mixture has the desired consistency. Add more oil if it is too thin and add more lemon juice if it is too thick. Same as regular mayo.
Add various flavors to bring it to taste. I used pepper and smoked paprika but you can make an aioli out of it by using garlic for instance or more lime to make a lime mayo...