How to maintain

If you know your average rate of loss, just do the math to calculate roughly how much you'll need to maintain. And yes, there is trial and error...but really, the difference between losing and maintaining is a preverbal handful of calories...like basically an extra snack or two or a bit larger serving at dinner, etc.

You also have to understand that maintaining isn't going to be exactly XXX Lbs...nobody weighs exactly XXX Lbs...body weight isn't static so maintenance is really a range, not a fixed number. For example, when I went to maintenance almost three years ago I averaged 180 Lbs...but it would fluctuate anywhere from 178 - 183 Lbs day to day...but when I tracked it on a trend line you could see that I was essentially maintaining weight.

You should also be prepared for a bump on the scale going to maintenance. As you've been dieting, your glycogen stores are in basically a constant state of depletion (not completely, but they're not full either)...when you eat to maintenance, your glycogen stores will top off (this is a good thing)...glycogen is basically fluid which has mass, and thus weight. You also have to consider that you will be eating slightly more so you will have more inherent waste in your system which also shows on the scale.

I basically do the same things now in maintenance going on three years as I did while losing...I eat a diet that is rich in whole food nutrition with the occasional treat here and there and I exercise regularly. I have slightly more latitude obviously, but for whatever reason people tend to think they can just go back to the way things used to be, and you can't...it doesn't work that way.

Although I do have my numbers charted to near perfection to calculate my maintenance, it's just a function of enjoying playing with numbers. In reality when I go through phases of maintenance I don't really focus all that much on that number. The main thing I go by is my scale. I weigh in daily and enter my weight into an app that calculates your trend weight and evens out the natural fluctuations. I give myself an acceptable range of 1 kg (about 2 pounds) over and 1 kg under my desired weight, and if I see my weight steadily climbing towards the upper limit, I eat slightly less, if it's steadily going down, I eat slightly more. It's much less complicated than it sounds.
https://trendweight.com

Since it's a moving average of 20 days, you will almost never see a sudden jump in your trend due to a few bloated days and panic, but you will be able to notice the general direction your weight is moving.

I'm currently losing weight, and you can see from my chart that the general direction is down and is predicted to continue going down (the dotted line). In your case, you will want it to be nearly horizontal.

Lost three and a half stone - so you have under-eaten by approximately 171,500 calories to achieve that.
(Well done by the way!)

Are you scared that you will accidentally over-eat that many calories without.....
A/ Noticing
B/ Intervening

It's exactly the same maths game whether maintaining, losing or gaining - just the goals differ.
Just set a goal range or upper intervention weight and enjoy your success.

Really there is no substitute for trail and error and then making adjustments based on actual long term trends as opposed to short term fluctuations.

That's the best part about all this.... do whatever makes you happy. Just stay within your calorie goals. For me, I increased my snacks.