I'm not opposed to a slowdown, it's absolutely a useful tactic, and could be used by those not in a union, I agree.

But we really, really need at the very least all unionized workers to commit to a general strike. That would be a little under 10% of the population, and a significant amount of them are in critical industries that virtually the entire country and most corporations rely on (Shipping ports, trains, trucking, healthcare, etc). Even if just those committed to a general strike, we could win.

Everyone else could join a purchasing boycott combined with a slowdown during that same time, but a general strike is the action that will cause the most fear in the corporate elites.

The website you shared talks about earning trust in nonprofits for months to set up mutual aid networks

That's if you don't have any existing mutual aid networks (mostly rural areas). But for anyone who has existing mutual aid groups, or a local Food Not Bombs chapter, you can join those and begin making connections immediately.

Setting up a union also takes time.

I have been publicly spreading the message to join a union for years at this point, personally. And we do not know exactly when a larger general strike will occur, it may be many months before it does, and in which time everyone who can should be starting to process to unionize by contacting a union now.