In any other way it is physically impossible. An ITX board is 170x170mm and a 120er fan 120x120mm. On one side we have the I/O area so the only way to fit a 120mm fan under the fin array is over the ram. The next limitation is the height. To fit inside the A4 the heatsink must be under 48mm (starting from the top of the CPU heatspreader).
Starting from the topside of the PCB we will have 55mm:
- 2.5mm ram socket
- 33mm LP ram
- 1mm fan clip
- 15mm fan
-----------------
3,5mm left (not enough for fins)
Starting from the topside of the PCB we will have 55mm:
- 2.5mm ram socket
- 18 mm VLP ram
- 1mm fan clip
- 15mm fan
-----------------
18,5mm left (enough for fins)
But if you mount the heatsink inside a bigger case you can mount a 120mm fan on the top side of the heatsink! The neccessary clips are included for all mount options: 92x92x15mm fan under the heatsink, 120x120x15mm fan under the heatsink, 120x120x15mm fan above the heatsink and 120x120x25mm fan above the heatsink.