As a Finn, probably just send out a message on some social media platform that people need to start turning on their saunas for the stability of the network. (Alternatively, like fingrid did, send a notification to my phone saying to "consume energy normally, as the pricing issue does not reflect energy availability")
Even a fairly small electric sauna is ~10 kW, so that's be just 10000 homes solving that problem.
Very few people get paid during this market anomaly. Most people have fixed rate contracts, and the few that do have variable rates, even fewer have ones where the negative price would be passed on to you.
Transmission cost and taxes will still be present, so this is more of a "hey it's going to be a societally good thing to go to the sauna today instead of tomorrow, consider it!" (Also, the saunas are definitely in use, don't worry, nobody's going to pass up the opportunity to say they went to the sauna for a good cause.)
Even a fairly small electric sauna is ~10 kW, so that's be just 10000 homes solving that problem.