How do you learn / train to use all (or at least more of) your time?
Regardless of whether I’m playing corr or live or blitz, OTB or online, I tend to play my moves too quick.
(I could have a week on the clock and still slam down a stone of remourse and regret in 4s 
)
IRL I think a good tip is not too pick up a stone until after you’ve definitely decided where to play. I find I want to pick up a stone from the bowl immediately and then stay too think about the move but once you have a stone in your hand, you just want to play it!
Online, no clue. Enable the submit button and use sheer force of will to ask yourself if there is a better move before you click it?!
Or maybe better, hand off the mouse until after you’ve definitely decided where to play. So you are less tempted to just click.
That worked for me on desktop, not sure what to do on mobile
Put the phone down?! That’s just generally a good thing to do anyway!
Huh. Neat idea. I might try that, thanks 
Thinking on, maybe you could try switching the screen off while you are thinking. Hear me out!
I recall an anecdote from someone I know who said when he plays (relatively strong I guess) people in Korea, they often look at the board a bit and then look away to think/read out moves. I suppose it’s good practice, even for mere mortals to visualise and I can see the advantage of not being distracted by the board position right in front of your eyes while trying to imagine alternatives.
I suppose it would only work with correspondence games and for me, I’d have to keep rechecking the board anyway but who knows,I think it would certainly slow you down!
If only I knew… I also tend to play live games too fast. Typically, an internet live game that goes to the counting phase lasts at most 40 minutes, except when it’s EGF rated (my last EGF rated game played online had 204 moves and was 78 minutes long). On the other hand, when using a real board I play slowly, even though I pick a stone from the bowl just after making my move. In correspondence games I waste a lot of time double and triple-checking variations before submitting my move. I can’t explain why.
Why should playing fast be a problem?
Because the clock is a resource and if I’m rushing my moves I’m not reading as deeply as I could be.
Often I play a move that “looks right” even if I have the time and ability to read that it doesn’t work.
Maybe a five minute meditation can help?
Training intuition/pattern recognition/shape knowledge is a viable alternative. Often there is no need to read.
(And yes, I know that’s not what you asked, but IMHO it makes sense. You should be able to trust your intuition if ut says “it looks right” and read only when it’s really needed)
I have also been wanting to improve my shape knowledge 
It’s not a problem if you like to play that way. It may be a problem if you make frustrating blunders too often, or if you want to break your habits and need time to consider other moves than the first one that comes to your mind
I don’t really suffer from this habit that much OTB, but online I need to be careful to avoid it. One advice I got in the past is to take my hand from my mouse and sit on it while I’m considering my moves.
I use the so-called “drink method” while playing OTB or in semi-serious online games
Thats the reason why you can always see me with some sort of drink in rl tournaments, in the morning its usually coffee or some caffeinated energy drink, in the afternoon its most often beer or wine xD
Of course the downside with this method is that you need to visit the toilet more often, and when you’re low on time it may seriously hinder your ability to focus on the game itself, but hey its better than blundering&losing the game with half an hour on the clock >___>
IRL if I have some cup or glass to drink by hand I tend to sip from the goke and put my fingers in my drink to get a stone. 
My advice is: