I learned the forward inside three in my good direction as a kid and it became second nature. I didn't really start trying the one in my bad direction until I was in my 30s and after more than 15 years of working on it, it still is a nemesis element for me.
Are you taking lessons? Group or private?
One thing that can help is to have a coach hold your hand while you try the turn. Even if you just rest one finger on their hand and they make no effort to help, that can give a tiny extra little bit of stability that can make a difference.
If you don't have a coach, try a friend's hand -- just make sure the friend can adjust their speed to your and stay steady on two feet.
To start out with you could try putting your hand on the wall while you do the turn slowly on shallow edges, but that will get you into some awkward positions (you'd probably need to switch hands once you get onto the backward edge) and once you try to do the turn really moving across the ice you need a support that can move with you.
A coach could also look at what you're doing that's causing problems and offer the specific corrections you need, which we can't do from miles away, sight unseen. They could also make a better evaluation of whether there's a problem with the placement of your blade.
Tips that help me in trying to get the FI threes on my bad side closer to the quality on my good side:
*Prerotate the leading (skating) arm and shoulder into the circle as soon as possible. When it's time to make the turn, think of the trailing (free) shoulder initiating the quick extra bit of rotation.
*Cross the free foot behind the skating foot as far as possible before the turn and try to keep it there during and afterward. (I find this is easier for me if I have the foot crossed wide and slightly below knee level, toe pointed, but I'm sure it looks awkward that way.)
*The skating knee action should be down-up-down with the actual turn happening on the up, a little further forward on the ball of the foot than the edges in and out on the downs. (Don't shift your weight all the way forward to the toepicks!)
And also get comfortable with the back outside edge from waltz jump landing, or forward outside three and change foot, or just pushing onto it from a standstill or from back crossovers. Find the checked position of the upper body that gives you control of that edge without the three, and then try to get right into that position as you exit the three.
Good luck!
