Resolving drip from flat roof over entry

[gfmucci]

I need to stop the dripping from a flat roof over my entryway.

I am considering fabricating an L-shaped thin aluminum flashing (from the roll material used for making gutters) , 4' long, 1"high. There is an adjacent gutter where excess water would flow into.

I could cement this new flashing either on top of the tar paper, or insert an inch or so under the tar paper. Which method is better? What type of roofing adhesive/sealant is best to use in either case?

 

[Snoonyb]

"L" flashing are already commercially available in 10' lengths.

 

[oldognewtrick]

What about hanging a small section of gutter instead of trying to secure flashing above or below the roofing material?