The easiest way to form a Dorian scale is to start with major and then lower 3 and 7. For instance, to get C Dorian start with C major and flat E and B.
D major has two sharps, and the notes that are sharped are 3 and 7. Lowering them removes the sharps, and you get all white notes. So the key of D is the simplest key in which to make a Dorian scale. Just use all white notes and keep D as the tonal center.
This is exactly what Miles Davis did for his composition, “So What”, one of the most iconic modal jazz pieces ever written. After an intro that is more complicated, he settles into D Dorian, stays there for around 16 measures, modulates up 1/2 step to Eb Dorian, then comes back down again. That’s not the whole story, but it’s the most important part.