How Do You Stop Blundering?

Stop blundering is very hard, I guess.

In my youth (round about 25 years ago), I had a very weird game. I had a won position and was material up. Then I missed a check. Nothing serious, but obviously I missed it. So I started active searching for checks or other things I could miss. But in that game, every move after the first , I overlooked the best move of my opponent (easy moves, nothing complicated, searching several minutes for it).
So I lost that game.

This was very uncommen for me. But in this game I understood, when other players told, that they had missed something completly. Luckily for me, I had this experience never again. Today I would react a bit better I guess. After my first miss, I would stand up, take a short break and hopefully, I would get my boardvision back.

To be honest, at that time I had a rating around 1400 and today I am around 2k. So I would expect that this blindness is much less likely than in that days.
I think it's part and parcel of the issue of visualising and predicting our opponent's strongest moves. Sometimes we fail to see our own candidate moves that are very strong, even for ourselves when the board is in front of our faces. It's obviously harder when you have to visualise what your opponent will have after your move (or in more complex cases, after 3 ply or more).

I really doubt this is something you can stop just by a routine process. You have to get better at generating candidate moves and better at visualisation. These aren't things to just tick off, they are fundamentals of becoming a stronger player overall.
i always try my best on not blundering.
oh and, btw, a read first the Ono blog and then i saw yours
I definitely haven't been completely successful at this and still sometimes blunder to this day, but three factors have helped me at least reduce the blunder frequency:

1. Understanding and reminding myself that playing tactically sound is way more important than following positional principles, because a single blunder just throws everything away and any single positional factor is usually worth less than a pawn, the smallest amount of material.
2. Being as focused as possible
3. Playing more long games, because then a blunder hurts even more and that is another incentive to avoid them.

Recalling how many won games have been won due to a blunder by the opponent and how many lost games have been lost due to a blunder by me also helps.

It may be kind of boring and frustrating, because chess has so many other interesting aspects, but it really is one of the most straightforward ways to improve as you don't need to learn anything new to do it.