You can cut the layered edge of architectural roof shingles and use the cut flat piece as your starter roof single.
How to shingle a roof valley with architectural shingles.
To secure the roof valley flashing nail it down carefully.
Apply a cover of starter architectural shingles.
Snap two chalk lines from the ridge to the eaves 8 cm apart increasing in width by 1 cm per meter towards the eaves.
Trim the shingles to these lines and cut a 5 cm triangle off the top corner to direct the water into the valley.
Nail the shingles 5 cm back from the chalk line.
How to shingle a valley with architectural shingles.
To shingle out of the valley with laminated shingles lay a shingle down as a gauge and mark the corner at the bottom left and top right of the roof.
Attach each shingle with three nails one in the center and one each on each side.
Instructional video on how to install a closed roof valley as part of installing tamko building products heritage series of laminated asphalt shingles.
Apply the first real course of architectural shingles so that the tabs reach the lower edge of the starter course.
I then move the shingle to the uppermost course on the roof plane line up the mark on the shingle with the valley center and again mark the corner.
Then starting at the base of the valley center your first piece of flashing in the valley.
After that correctly positionthe first shingle and properly snap a line of chalk across the roof to mark the top layer of the shingles.