Dry fire, especially without any kind of target.
With an empty gun and a safe backstop, align the sights - they need to be seen perfectly, with the same amount of light on all sides. Don't focus on anything but keeping those sights aligned - don't look at what you are trying to hit, or anything else, which is why this is best done without any target. Something like a big blank wall is perfect.
Now, maintaining that hard focus on perfect sight alignment, begin pressing the trigger. The goal is to do it without any impact on sight alignment. Again, don't worry about keeping the gun pointed at any particular "target" - it's nothing but sight alignment and trigger pull. Practice until you can pull the trigger all the way through without losing focus on the sights, and without the sight becoming misaligned.
When you can do that on demand, head to the range with a supply of notebook paper or blank cardboard. Or even just use the back of regular targets, if it doesn't make it feel like you're "wasting" them. Start with the same dry fire drill at the blank page. When you've got it grooved in again, try it with a live round. If you've done it correctly, the last thing you saw before recoil was perfect sight alignment, because you were focused on nothing but the sights, and carefully pulled through the trigger without disturbing anything.
If that's how it went, keep firing the same way - one perfectly controlled round at a time - and you can keep shooting as long as that works. If that's not how it went - or if it works for a while but then you find yourself "peeking" at the target or otherwise not paying the sights your full attention - then do some more dry firing.
That, in a nutshell, is 90% of slowfire shooting. If you master it, you'll be a better handgun shot than the overwhelming majority of shooters.