Your belief is correct! The contract work I see seems to fall into 2 buckets: short term gig, or temporary 40/hr per week. I'm looking for a some kind of middle ground: long term 8/hr week.
I think you'd need to be a specialist and advisor in something that a company needs and currently isn't good at.
I mean, if you're a company and you want some development done, you probably don't want it taking 5 times as long as it need be. You'd rather hire someone 5 days a week (even for a short period of time) rather than someone 1 day a week.
But for advising the teams companies already have about something they don't know about but you do, it could still make sense for the company. E.g. for a while I helped quite a few companies do MySQL 4 to MySQL 5 transitions (a while ago now obviously!) It was something I became quite good at but companies didn't want to build up the internal knowledge because they only needed to do it once. I would come in and discuss their situation, advise them, come back a bit later to see how they were getting on and review what they'd done, etc.
Focus on things you're good at that other companies might not have knowledge of. Particular programming languages, particular tasks such as optimization or software design, particular databases, particular clouds perhaps. Or migrations and transitions where it doesn't make sense for the company to build up knowledge as they only do it once.
Yep, this. Consulting is probably the only option. Though that said, in my experience, consultants are short-term positions at any given company, not long-term. You come in, consult, advise, and then ensure the changes take hold -- then your contract is up. Although my experience is rather limited in this regard, so maybe there's a long-term opportunity hidden in that industry somewhere.
Good luck finding that, but I don't see many employers being good with a schedule like that for a contractor or employee. At best, you might be able to get a paid internship with those hours, but (a) it won't be much of a paycheck, and (b) they'll probably expect you to become a full-time employee at some point, and won't likely hire you even for an internship without that possibility.