How do you fit a heatsink onto a caseless P3?

[Nex]

I've been informed a good practice for cooling is remove the plastic backing case.
However, I have an Alpha P3125S Slot 1 heatsink and I don't know how to fit it without the case. There won't be enough 'width' without the case to fit it.
Is there anyway this is supposed to be done?
I should just obviously add I'm using a Slot 1 P3...

[It_The_Cow]

The way I did it, I just used a jigsaw cutter and cut out the the spacers. You can also use the ends of pens, but I found my way to be easier