The answer here is pretty simple — you take money, resources, etc from people who don't reproduce and you redistribute them to the people who do until the population stops declining.
But even if you do that, you'll have an issue in a generation or so when those childless people are old. They're retiring, they're drawing from pensions and social security programs, they're using the hell out of the medical services, and someone has to pay for that. They don't have kids to take care of them, so all that capital that went towards the children gets siphoned from them in their working years. Now they're in a situation where they can't afford kids, and that trick can't be done anymore. It won't actually get population growth up over a few generations.
As an added bonus, in accomplishing this task society actually becomes worth participating within, and people might naturally wish to bring a child in to this crazy... crazy world.
But even if you do that, you'll have an issue in a generation or so when those childless people are old. They're retiring, they're drawing from pensions and social security programs, they're using the hell out of the medical services, and someone has to pay for that. They don't have kids to take care of them, so all that capital that went towards the children gets siphoned from them in their working years. Now they're in a situation where they can't afford kids, and that trick can't be done anymore. It won't actually get population growth up over a few generations.