There are lots and lots of common yoga moves/general exercises where the intention is to activate and stretch out your primary hip flexors (the iliacus and the psoas). These get chronically short and weak when we spend lots of time sat down on chairs.
However, it can be confusing to know whether or not you are truly waking up your iliapsoas, because, if they are super weak, lots of other muscles/joints close by will work too hard (compensate) on their behalf, so you never actually wake up the hip flexors. Once you actually wake up your hip flexors without compensating, you'll find they start to open up and stretch out much more readily!
In this video I walk you through a classic 'hip flexion' exercise which is commonly performed in such a way you're not actually waking up your hip flexors.
Listen to all the cues and let me know how you get on!