Theres some really fabulous advice here. I too have been WFH since March of last year and have put some measures in place for my own sanity. If you arent careful then you feel like you are living at work, not working from home.
My house is very small with no space for a proper desk. I work on the sofa but using one of those desk things that you can sit with your legs out under (a bit like for eating on in a hospital bed!). I put everything away at the end of the work day, its part of the boundaries - getting it out in the morning and putting it away at the end of the day really helps. As an insomniac, I couldnt work from my bed. I would probably work on the bedroom floor in a pile of cushions if that was the only option!
I cant face food early so I use it as an opportunity to take a quick break during the morning to make some scrambled eggs, fried egg on toast, porridge, cereal etc.
Fresh air is vital for me so unless it is absolutely freezing, I have the door open (for the dog!) pretty much all day long and a window open if not. I like to light a scented candle or have a wax melt going while I am working, I only light it during work time to again help to demarcate work time and home time.
I dont smoke and therefore get regular breaks from my workspace so I write a little schedule of my day first thing and factor in my calls etc for the day and then work out when I will take short breaks. You arent tied to the desk all day long when you are in the office so you shouldnt be at home either. During those breaks, I might have a quick stretch, give the bathroom a very quick wipe down, wash the dishes up and put them away after lunch, step outside for some fresh air etc.
I make extra at tea and have it for lunch the next day (I have always done that, even while in the office). No time spent preparing and no having to think about what to make.
After work I hoover the living room. Dont laugh, I have a very sheddy dog and without it my grey carpet looks whiteish (dont be jealous). It makes the room looked better but also makes me think that the working day is over now it is a habit. I then take the dog out but with no dog I would wrap up and head out anyway. I love it when it is windy the best, I literally feel like it is blowing the day away :)
I like to bath/shower at the end of the day rather than the morning but that can form part of your routine too.
I HATE cleaning if I am honest but I love having a clean house so each day when I hoover the living room I also do something else such as a quick dust, or a hoover upstairs etc. It helps me keep on top of things.
Try reading 'The Miracle Morning', its supposed to be really good :)