Keep your arms straight and your body straight at all times, with one leg straight and one leg tuck to your chest.
From a hanging position, lift the body into one-leg front lever, then into inverted hang, and on to one-leg back lever and German hang.
Then reverse the motion.
The primary muscles work equally regardless of which leg you extend, so it is not necessary to count the exercise as unilateral: it is enough to alternate the legs with each set or repetition.