On longer walks can work well,
But for me before bed has worked the best. My bedtime routine with my son is that he does half of the stuff and then I do half. He picks my half, I pick his half.
I pick a simple reading book, a few maths cards (with sums on them), and anything else he is learning/doing at the time, that I want him to do.
He picks a pile of story books/comics etc. that he wants me to read.
He reads through all of his reading/maths, and then I read through the pile of stories he has picked out, then bed.
I know it isn't a really normal way, but it works really well. It feels very "fair" to a kid, so you don't get a lot of complaints, and it gives him a bit of autonomy which is always nice. But generally it has just proven a really easy way to get a bit of reading and a bit of maths in every day, which is especially important for me because I'm not in the UK and my son doesn't learn English reading at school, so it all has to come at home.