I do this same type of stretch (pretty sure I know the one you mean) only while standing and putting the front of my thigh on my balance ball, then bend the other (standing) leg. I find I feel it gets my leg out more, with no pressure on my knee, and because the ball has a little give, I can slowly dip in as much as I need to. Use desk or pole to help with balance on this one. I really tried to get a foam roller routine in place with my workout, but I haven't quite gotten to incorporating it regularly. I also like to stretch my flexor standing by pulling my foot up behind me, much like you see in classic yoga poses. Once you've got that foot, you can just lean forward a little to get the effect of being in a split on the floor with your back knee bent, only you don't have to be flat to get a good stretch and prep for floor flatness. I also like to lie on my belly, grab both my feet behind me, and lift as high as i can. Its stretchy when using more arm than leg, strengthy when using more leg than arm, and strengthening and stretching for back flexibility all at the same time. I started really focusing on flexors when I realized the only time I was in a full split, I was practically kissing my front knee. Slowly sitting up wasn't helping because I wasnt interested in pulling anything, and its easy to let your back leg cheat out when going this way. I hope that helps, I'm sure there are tons of other things people do for this. I even like the one where you pull your foot to your butt while standing, but I love to sit on my feet, lie down backwards, and just SLIGHTLY lift my hips. Its like the same stretch, only more intense, and getting both legs at once. Just make sure not to turn your knees in or out or do anything funky with your joints and things. If you have a strong buddy, you can lay on your tummy, have them stand over you facing your feet, they grab your feet, and slooooowly walk backwards. Just make sure the stretch is in the front of your legs, and they're not stacking your weight on the small of your back all curled over. You have to be able to let them know when to stop, and you have to be able to use your back muscles to protect your back while allowing a stretch in the legs. Talk about a rubbish explanation LOL!!!! I hope you can picture most of what I've said.