Extensions need to be applied 1mm away from skin. This gives room for skin on lids to rest without the poking of extensions. This also gives adhesive room for adhesive to flatten, spread backwards, and have space to dry.
For competition: application space is .05 mm
Application does not matter how many fans are applied to natural lash but the rules are the same: make sure the base is blended with the NL.
If extensions are created with boxy bases or bases that are not wrapped or unevenly applied, clients brushing uneven lashes from base to tip will pull and tug on the base of the lashes. The brushing stimulation will cause signs of traction alopecia.