Taking My Time

I'm essentially a beginner; I had a decades long absence from chess.  I carried over my provisional rating from long, long ago .... when unrated players were given an initial rating of 1200.  I have nine rated games to go to establish an actual rating.  I've played in one tournament since my hiatus and my rating dropped (another) 100 points.  At this point, I estimate I'm playing around 700.

Various texts emphasize that beginners should learn to slow down their play.  They recommend avoiding blitz chess and recommend not playing games faster than G/30 on Chess.com -- preferably longer.  The gist of the advice is that, if you take longer to move, you'll look at the whole board and analyze more deeply.

I have discovered I play way, way too fast.  I turned on the timer for puzzles here at Chess.com -- where I'm stuck around 700 -- and saw that I was making the majority of my moves in less than 20 seconds, often at 15 seconds, and as low as 12 seconds.  But, without the timer, and even with it, my time to move seemed, subjectively, significantly longer.  I've also learned that if I force myself to take a really long time -- 2-3 minutes -- I do better.

So, although I know I must slow down, and can do so for several moves, I find myself playing faster and faster.  I know where I have to go, but am having difficulty getting there.

What methods do you  use to keep your moves at a slower pace?  Any advice?

...i have the opposite problem! :/