Pistol squats and sumo-style barbell deadlifts today. Getting rock-bottom on pistols ... standing on a platform. This allows me to concentrate on depth without having to worry about extending the free leg, given my chronically-stiff hamstrings. The platform allows me to dangle the free leg a bit.
However, I do intend to lower the platform next week. And hopefully, in not too many weeks, I'll be doing a legit pistol from the floor. No, it'll never be postcard-pretty, what with my hamstrings. But I'll be happy.
Before doing pistols and deadlifts (and perhaps I should do it more often) is a bit of a quirky ritual that is perhaps as beneficial for the psyche as for the joints. After a brief mobility circuit which includes glute activation exercises, I do full bodyweight squats, really settling in at the bottom. Then I duck walk in all directions. Finally, I get down on the floor cross-legged, without the use of my hands, then get up from the floor without the use of my hands.
In addition to really prying open the hips and waking up the glutes, it acclimates me to the 'down position', which I find us useful for pistols in particular. In any case, it seems to help with my anterior knee pain.