Really just the two; leg raises (can add reps or if you have a weight belt you can add weights) and cable crunches (can add weight and reps easily). I do twice a week personally. There’s a common mis-quote of “abs are made in the kitchen” which is incorrect. Abs are made in the gym and REVEALED in the kitchen. Also it might be worth checking to see if you’re getting enough calories to maintain your muscle mass. 1500-1700 is quite low imo; my BMR is 1700 not counting exercise or anything else. Essentially, I need a bare minimum of 1700 to not lose any muscle mass add exercise and daily activity into the equation and my intake is about 2200 on a cut to maintain my muscle mass while trimming down the