Number the cubelets from 1-27, starting from the end that has a 3-cubelet segment followed by a 2-cubelet segment. Here, then, is the location of the cubelets in the finished cube (and 1-27 is the order in which they need to be put in place):
27 8 21
26 7 22
25 24 23
12 9 20
13 6 17
14 15 16
11 10 19
4 5 18
3 2 1