Where there is either no fascia or detailed crown molding or a severe angle, we use a hidden strap system. The support brackets are mounted underneath the shingles. The gutter straps are secured from the gutter brackets to the support brackets. We try hard to avoid installing straps over the shingles.
Where the fascia is at an angle, we use an aluminum wedge to make up the difference in the angle of the fascia. These wedges are behind the gutter.
Where the fascia has a step to it, either flat or at an angle, it’s possible that w.e would need to use wood buildout to fill in the step. We use either pre-primed and painted wood or composite material