It's important to see that these aren't mutually exclusive, even though they sound quite contrary. On the one hand you have the
hack -- the one-off prototype thrown together simply to verify what can or can't be done. On the other hand you have the
design -- once you know what perspective is best, to build the system from that perspective and validate that your intuitions are building one coherent whole.
Kay's Law is that the right perspective is worth 80 points of IQ: that is, if you find the right way to look at a problem, you can do things with the ease of someone with a 180 IQ who didn't have the advantage of that perspective. How do you get a good perspective? Well, there are a couple different ways. Some are pre-made perspectives: for example, dynamic programming: "let's just build up all the solutions in order from n=0, reduce everything to some other problem we've already built up." Some are intermediate, like wishful thinking: just imagine that magically, you have functions which you don't have, so that you write an algorithm which is correct, but references a bunch of functions which don't yet exist.
Some approaches to new perspectives are more general: hacking, for example, is when you try a bunch of things which just barely work, to find one which does. Another is duck solving: explain your problem out loud to an inanimate object (like a stuffed or rubber duck), and half the time you'll accidentally create a perspective purely for explaining the problem which is useful for solving it. These are very generally phrased because "problems" are a very general topic for intellectual discourse.