The correct way to flash at the shingles in thearea you indicated is using step flashing.
Roof flashing above or below shingles.
Coat the flashing with a zinc based primer followed by two or more coats of spray on rust preventive metal paint.
Step flashing consists of short pieces of flashing each installed to overlap the shingle in the course below and to be overlapped by the shingle in the course above.
Step flashing is made up ofshort pieces usually about 5 x7 that are bent in half the long way.
All shingle manufacturers require step flashing at sidewalls for both asphalt wood and slate.
You may want to paint the flashing to match the roof.
First step flashing must be installed before the siding so that the siding can cover the top of the flashing.
Each piece is slid under a shingle tab going up the roof.
With that type of flat edge flashing the shingles should have overlapped 2 additional courses until they reached the lower edge of the flashing or at least past the penetration of the roof sheathing.
Any issues here roofer guys.
The main purpose of the drip edge is to direct the flow of water away from the fascia board and to help protect the rakes and eaves of your roof.
Shouldn t the shingles cover the flashing instead of the flashing covering the shingles.
First use a stiff wire brush and solvent to clean the surface of any dirt debris or corrosion keep solvent away from asphalt shingles.
If this is a repair job the siding must also be removed and replaced with the flashing.
Joe same type of flashing here but these guys went with 1 additional course of shingles which is still wrong.