Add egg yolks, garlic, lemon juice and avocado oil to a 2-cup glass measuring cup (or other container that is just large enough to allow the head of your blender to reach the bottom). Place the head of an immersion blender on the bottom of the pitcher; turn it on to its highest speed. When you see aioli beginning to form, slowly lift the blender head from the bottom and move it up and down and side to side until all of the oil is incorporated.
Add olive oil in a slow, steady stream, whisking constantly until emulsified. Whisk in salt and serve or refrigerate. Store refrigerated in a sealed container for up to 2 weeks.
You may want to transfer the aioli to a separate bowl before whisking in the olive oil and salt.