> If I post a job with 4h a day which amounts to 1/2 of a normal salary I will probably never get a candidate.
I think you're mistaken about that. If you can persuade candidates that it really is 4h a day at 1/2 of a normal salary, you will get candidates who are excited by the job because it opens up their time for other opportunities for hobbies, home life, side projects, open source projects, looking after family, other consulting gigs, education, etc.
However, for developer roles you might find that potential candidates don't entirely believe the ad. I think they'd imagine the employer having unrealistic expectations of what 4h reasonable output looks like, so that they'd feel pressure to work overtime, resulting in closer to 8h anyway while pretending to get it done in less, for 1/2 of a normal salary.
Persuading candidates is where it breaks. I don't have time for that, we need to hire now and if we hire someone then for next 2 years we probably won't hire anyone new, and I don't think there is enough people who would like that 4 hours. I also have to pay for ad that will get most CVs
It would be much easier if I get someone CV and he writes cover letter explaining that he would like to try such an arrangement.
I tried to get part time dev for Kibana/Elastic needs like 4 hours - anyone I approached was not even willing to discuss "why" they just said no. People also don't have time to listen to your persuasion, most of the time it is clear cut and goodbye.
I think you're mistaken about that. If you can persuade candidates that it really is 4h a day at 1/2 of a normal salary, you will get candidates who are excited by the job because it opens up their time for other opportunities for hobbies, home life, side projects, open source projects, looking after family, other consulting gigs, education, etc.
However, for developer roles you might find that potential candidates don't entirely believe the ad. I think they'd imagine the employer having unrealistic expectations of what 4h reasonable output looks like, so that they'd feel pressure to work overtime, resulting in closer to 8h anyway while pretending to get it done in less, for 1/2 of a normal salary.