Another thing that can get in the way is if you have generally quite a chaotic environment around or don't have things set up for success. I call this the "ADHD domino problem".
For example, it might take me an hour to make some sandwiches and wash up, if I first have to locate a lunchbox, oh, none are actually clean so I need to clean one, the sink is full of dirty dishes, got to move those, the drainer is full so just put those bits away, they're dry now, OK I've moved the dishes from the sink but it's a bit rank with spilled milk from this morning and bits of last night's dinner, scrape those into the food waste, need to clean the sink first, there's some issue wit hot water generation that I keep meaning to get fixed but haven't got around to yet so it takes a while to fill the sink after it's cleaned, now I'm washing up, but my sleeve got wet and I hate that feeling which is making me irritated, do I run upstairs and clange my top or just roll it up and hope that it will dry? Wow there are a lot of dishes, I really should have done some last night, this is a very stubborn stain now which is hard to get off, that's annoying.
Right the lunchbox is clean, find a tea towel, dry it, what to put in it, oh we've run out of bread, I wonder if we have any wraps? Yes this wrap is OK, now I need to sort through which bits of veg are OK in the fridge to put in it, I really must have a clear out, what did she like again? I can't remember what the current phase is, oh I got those cheese strings for school lunches but I'm not sure if she liked them, I'd better go and check. While in living room talking to DD I notice that there are some more unwashed plates so bring these back through to kitchen. I've finished the lunch, need to move a couple of things to make space in the fridge to store it. Oh yes, must get today's lunchbox out of her bag, throw away the wrappers, they ping instantly out of the bin as it is too full. Still have to finish the washing up. Check time and it's been an hour.
vs
Select clean lunchbox from stack of clean organised lunch boxes which is near the cupboard that I keep the lunchbox snacks, there are plentiful snacks and I don't have to decide what to put in because I'm following a formula that I do every day, there is enough bread/wrap/veg and there isn't any old expired food cluttering up the fridge being in my way, I have a nice empty clear space to prepare the lunch so this takes about 3 minutes, close the lunchbox, place in the fridge which doesn't need rearranging.
While I was doing all this I have been running hot water (which comes out at a normal speed) into the sink which is already clean and I wash up the lunchbox from today plus my travel coffee mug and maybe one item which got left last night as there wasn't space/time. Or given there are so few items I might not even bother filling the sink. The breakfast dishes were washed this morning and last night's dinner things were done then. After washing up, I wipe out the sink and leave things to dry.
Takes about ten minutes. (Fifteen if you did leave the breakfast things for after school). BUT you have to have a lot of other things in place first. People with ADHD tend to not have these things in place which make life easy and smooth, so everything feels complicated and difficult.