The obvious solution is artificial wombs, but that is probably very far in the future. But since you're talking about who the future belongs to, that's who. Until then, probably low population density already-developed countries that have fairly open immigration policies to accept the children of foreign breeders. That has seemed to mostly mean the US for the past few centuries, but places like Canada and Australia could easily employ similar strategies.

Even short of artificial wombs, there is a lot that can be done to help with this. The real issue isn't that women don't want to have kids at all, ever. It's that if they enter the labor force and work full time, usually it gets put off, often until it's not exactly too late, but at least too late to have as many children as you might have if you'd started earlier, bringing down the national birth rate because too many would-be mothers have aged out. There could easily be medical solutions to that focused on making pregnancy more viable in late middle-aged women. Better prenatal care, cheaper treatments for infertility. Even non-medically, it could just be more flexible working arrangements like you mentioned, work from home, better and cheaper daycare, more generous universal leave policies that don't single out parents, possibly something like sabbaticals that universities do but for commercial ventures, too. Mandatory paid gap years for people in their 30s even if they don't have children. A country that pulls that off could keep the economic advantage of having a larger workforce talent pool to draw from without sacrificing internal population growth.

Obviously, private employers can't bear that burden and it would need to be subsidized by the government, but if you really believe there would be significant national strategic advantages to doing this, then it should be subsidized by the government.