The L-sit hang is technically not so difficult to perform, but you will notice that this static position is pretty hard to hold for a few seconds. The L-sit hang is very effective for your abs and core. While hanging on the bar you also train your arms and shoulder. If you prefer similar but more dynamic moves, then have a look at the hanging leg raise or hanging windshield wipers.
How to do a L-sit hang
Hang on a bar and slowly raise your legs in a 90 degree position as pictured below. Hold this position as long as you can. If this is too heavy for you, than you can first try to raise one leg or you can start with your knees bend.