I just happen to have an example handy...
I use Dirko. You can put one of these together with Dirko, bolt it in and run the saw right away with no problem. I still bolt it together outside the engine housing for the main reason of doing a leak check before committing to complete reassembly..., especially aftermarket kits or cylinders. The machining and casting is all over the map with the cheapy kits and cylinders and more will leak than not unless excessive sealant is used. Some say to always use the old OEM bottom pan but I've found using the pan that comes with the cylinder can often be a better match for the seal pockets. Regardless, it's nice to know you have a completely tight shortblock beforehand than finding out the hard way there's a leaky seal once the saw is back together AND you have that damned bar stud screwed back in! BTW, I just use Gorilla tape to block off the intake and exhaust ports for a quick vac/pressure test outside of the engine housing. Works fine up to around 5~7 psi and 12~15 inHg which is all that's necessary anyway. Intake and exhaust surfaces just need to be nice and clean for a good seal. I use a little alcohol. Another good reason for sealing outside the housing and letting it completely set up is for ease of getting the assembly back into the housing itself. It's just easier when you're not trying to keep the pan from sliding around while also trying to position the assembly.