Or, equivalently, they can print $10 bills and hand them out to people. Simpler that way.

In practice, of course, it is preferable to give people jobs to do in exchange for their $10 bills, like fixing our broken roads or sewers, or building nice public infrastructure. That way we keep our workers and factories in practice, and we don't waste productive capacity, and we distribute the money according to fair rules, and we get some nicely paved streets.

But when you have to stimulate the economy and you're desperate you could literally "fire up the helicopter" (as the metaphor goes) and start dropping dollar bills from the sky.

Unfortunately, the Federal Reserve may not be able to do this. Deficit spending takes an act of Congress, and for various terrifying structural and political reasons the US Congress has punted on the problem of managing the economy.