In my region, where the number of hours worked annually is 1800+ as per OECD, it's quite simply difficult. Employers expect full time availablity and would rather not have anyone fill that role than allow for this.

My friend managed to do it by boiling that frog via taking Friday afternoons off. Everyone was happy with that arrangement, so he started taking entire Fridays off. Then he switched to Mondays.

Meanwhile my SO got a hard "no" on any amount of reduction. She's looking for a part time job, but it's not something employers normally advertise.