the way i did it was as follows, not saying its the best way but it worked for me.
loosly install bottom ring half to base using the screws (personally i would loctite these screws as if they loosen you have to strip everything off to re-tighten them (including take scope out of rings).
Tighten screw enough that the ring half is not flapping but you can turn it easily
now you will need the flattest surface you have in the house, kitchen worktop with a piece of plate glass on top or a decent piece of flat steel will be ok.
Place the bottom ring half/base unit on the flat surface such that the back edge of the base is one contact surface and the edges of the bottom ring half are the other contact points, so it will look like a pyramid shape.
This will ensure that the ring half and the base are mounted at exactly 90 degrees relative to each other in the axial direction, as Sako/Tikka did not see fit to include a pin to help here.
Now, maintain downward pressure on the "tip" of the pyramid while tightening the retaining base screw, this will ensure that the pieces remain in the correct place, otherwise there is a tendency for the screw to try to rotate the ring half as you tighten it.
Perfect alignment is not absolutely vital as the design of the polymer ring inserts will accommodate some deviation of the ring but im a perfectionist (maybe a tad anal!)
Once you have done the above, slide base units onto the dovetails and push them as far forward as they will go, dont beat them but good finger pressure/a gentle tap with a wooden block will seat them fine. torque screw to spec, or just do up tight.
Rest of the scope mounting is as per any other scope, just make certain your hex key is a good fit (7/64 i think but check!) i had no issue with my optilock but many cite the ring screws especially as being soft.
This is the method i used for my tikka and im fairly sure that it is basically the same for the sako, but the sako may have tapered dovetails, in which case just double check which way the base will fit on before sliding it on.
hope that helps.