cutting/glueing baffles, diy sump

[hqgc]

I'm taking a crack at building my first diy sump and I had a few questions...
1.How much smaller do you cut the baffle (width) then the inside of the aquarium?
2.Is there a way to "temporarily" tack the baffles while you silicone?
3.How the heck do you silicone in between the one inch space if you build bubble traps?

Thanks.