Agree with pomodoro - here: pomofocus.io/. I refer to it as productive skiving - if I'm forced to wait for that 5 minutes 'break', it makes me get things done.
Starting the day with even a 5-10 minute walk outdoors regardless of weather.
No social media or phone use (unless for work) when I first wake up - something about the scrolling destroys my attention span.
Set out a little morning routine - I get out of bed, set coffee brewing, go for my silly little walk, come back, coffee and then when I get to my desk upstairs the very first thing I do every day is start a new to-do list for the day with all my meeting on and anything I didn't get to the day before (helps to have something to physically cross off - a whiteboard is a great idea actually!). That way it gives my brain chance to go 'oh, we're doing the morning routine, must be work time now'.
Try and organise my meetings for afternoon - that way I can get into work in the morning and by afternoon when all I want to do is piss around, I have to focus because I've got a load of people peering at me on Teams.
If I've got loads to focus on and really need the boost, a Flown session helps - flown.com/. This is where you go on a video call with a load of people, set out (vaguely, if needed for confidentiality purposes) what you need to do, and then silently work 'together' for a while before you reflect on whether you've achieved it at the end. Obviously v much depends how possible that is for your job (and there's sometimes a bit of happyclappy motivational quote stuff which isn't for me), but largely it's a godsend for me - it's called 'body doubling' and it helps a lot with procrastinating.
All work for me and my very scrambled egg ADHD brain!
I love my job very much, but I'd say I spend far too much time procrastinating (at work or at home, but obviously easier at home). Thankfully as a workplace we're focused on results, not time worked, so as long as stuff gets done it doesn't matter. But there's a widely-quoted study that said office workers are working on average 3 hours a day - now whether or not that's accurate (can't imagine lawyers on 5-minute billing slots are doing that!) it shows that people are generally procrastinating more than you'd think. It's just more guilt-inducing at home, I think - in the office, you're still there physically if not mentally.
Can you go into the office more at all? I used to love WFH full time but I've found now I go in some of the week I appreciate my WFH days more and get more done, rather than them just stretching out.