In the year 2005 or earlier, an Edward D. Collins, wrote the following procedure "How to Create a Fischer Random Opening Position".
The pawns go on their original squares. The pieces will be placed randomly on the back rank, subject to the rules of Fischer Random chess. The bishops must be on opposite colors and the King must be between the two Rooks. For each of the first five steps below, simply roll the die and act accordingly to place the white pieces. After placing White's pieces, Black's pieces are simply a mirror image.
Step #1 Select a black square for the bishop
If you roll a 1 place a bishop on a1.
If you roll a 2 place a bishop on c1.
If you roll a 3 place a bishop on e1.
If you roll a 4 place a bishop on g1.
If you roll a 5 or a 6, roll again.
Step #2 Select a white square for the next bishop
If you roll a 1 place a bishop on b1.
If you roll a 2 place a bishop on d1.
If you roll a 3 place a bishop on f1.
If you roll a 4 place a bishop on h1.
If you roll a 5 or a 6, roll again.
Step #3 Place the Queen on the empty square of the number that you roll.
For example, if you roll a 1, place a Queen on the first
empty square. If you roll a 3, place the Queen on the third
empty square.
Step #4 Place a knight on the empty square of the number that you roll.
Again, for example, if you roll a 2, place a knight on the second empty square. If you roll a 6, roll again.
Step #5 Repeat Step #4 for the other knight.
If you roll a 5 or a 6, roll again.
Step #6 Finally, place the King in-between the two rooks.
This procedure creates any of the possible 960 opening setups with equal probability.
EDIT: The source is http://www.edcollins.com/chess/fischer-random.htm