Because one of the things that makes something “easy” on the guitar is the presence of open strings, let’s take a closer look at a few flat keys and see how many standard-tuning open-string notes can be found in the keys of Bb and Eb.
Excerpted from Weekly Workouts: Flat Keys and Open Strings | by Scott Nygaard
To get you started, and to convince you right off the bat that you can indeed play a Bb major scale using open strings down near the nut, the first workout is a simple ascending scale pattern that begins on the first fret of the A string and works its way up to the first fret of the high E string before returning in a mirror of the ascending pattern.
You’ll notice that once you get up to the B string, your fretting hand has to work a bit more, because the open B and E strings are not in the key of Bb.
Measures 13–18 show a simple “broken thirds” pattern in Eb. Once again, there are no open strings available on the top two (B and E) or bottom two (E and A) strings, but you can probably see how you could find some melodies using the middle two (D and G) strings if you find yourself in the key of Eb.