The bottom row is the trickiest reach because your fingers curl downward. Keep your wrists still and let your fingers do the moving. After this unit you'll know every letter.
Index fingers reach down: left to V, right to M.
Middle fingers curl down to C and the comma.
Ring fingers reach down to X and the period.
B is a long stretch for the left index finger; N is a short reach for the right index finger.
Pinkies curl down to Z and the slash. Now you know every letter key!
Common words using the whole alphabet. Focus on smooth, even keystrokes.