The problem with water, is that you pretty much have to destroy it if you don't want it raining, seeping or channelling back into the oceans.
So let's do that.
First, an assumption: that humans have perfected the nuclear fusion reactor - not just for fusing hydrogen, but for fusing any element. We can fuse all of the elements up to iron and still release energy. So our approach has the handy side-effect of releasing a lot of energy, which we are going to need.
The first step is to gather up water and split it into hydrogen and oxygen, using plain old electrolysis. We're then going to burn the oxygen in a fusion reactor. Not an easy task, given the extraordinarily high temperatures and densities that are required to achieve this in stars - we're talking much, much higher than the kind of fusion reactors that we already struggle to build today. But hey, according to our assumption we've managed to solve that engineering problem.
We could perhaps let the hydrogen go and hope it escapes the atmosphere, or we could burn that too. Since 88.8% of the mass of water is the oxygen, we'll assume that if we can solve the oxygen disposal problem, we can solve the hydrogen disposal problem too.
OK, so each O+O fusion reaction releases 9.593 MeV of energy, and gives us a silicon atom. Cool! We can use that silicon atom to bind some more of the oxygen into quartz. This provides a shelf-stable product that can be used to build more land, or just pile it up into a new mountain somewhere out of the way.
How much oxygen do we need to burn to achieve our goal? Let's assume we only need to burn 50% of the oceans to achieve the desired sea level drop. That's about half a quintillion metric tonnes of oxygen - or about 10^45 atoms worth, according to some rough assumptions about the ocean's mass that I found. But I only spent about 20 seconds googling, so double check this before proceeding.
Did I mention that not only will we need an advanced oxygen-burning fusion reactor, but it will need to be a really, really big one? Or perhaps a number of smaller ones. But at any rate, we've got a lot of fusing to do. The great thing about fusion is that you get energy out of it, so you don't have to worry about how you're going to power all of the operational concerns like gathering up the water, moving it around, splitting it, and so forth. You can definitely assume we'll have enough energy.
But might we have too much?
If we burn all this oxygen, we'll release about 10^34 joules. That's approximately equal to the total energy output of the sun each year. This would definitely set the entire planet on fire, which probably meets the goal of creating "newly exposed lands", though the "new political entities" would have to be of a hardy variety.