It can sometimes be difficult to keep a large, delicate gasket in place while the second component is fitted. If that’s the case, I may decide to use a smear of sealant as adhesive. But which side to stick it? Because gaskets do sometimes rip when being removed, I consider how difficult it will be to clean off in future; I’ve found it’s often easier to clean the remains from the component which will be removed, such as the cover in your case, so I might prefer to stick it to that.
I’ve just refitted a modified cylinder head to the three cylinder engine of my supercharged trials car. I have reduced the CR by fitting an aluminium decompression plate. I had to “stick” the plate to the cylinder head with Wellseal and also use a small amount of it to hold the head gasket in place below that, while I turned it the right way up and lowered the head onto the block. Normally the gasket would be fitted to the block and the head fitted onto locating studs. On this engine, there is nothing on the block to locate the gasket with (it has long through bolts fitted from above) and I was very concerned that I might misalign it then damage it. Quite tricky
Built like a gun... could go BANG!