Challenge your abs, hip flexors, and even the neck musculature with this combo exercise. Simply maintain the half sit-up position while performing flyes.
Anchor your feet and lean back until you feel your abs engage. You can use a lighter weight and do the exercise in a timed manner for 60 seconds, or use heavier weights and go for 10-15 reps. Keep your spine and neck as neutral as possible.
A conventional barbell is fine, but if that's all you use you're missing out on strength gains and a little novelty. Change your bar to improve your training.