Why can't it be "they are my boots"?
Why can't this be translated "those are my boots" ?
Why doesn't "ce" agree with "bottes"? What's different about situations where one would use "ces"?
Have a look at this - it may clear a few things up.
Shouldn't it be "ces sont"?
We could say it's as if "c'est" = "ce est" (but it would be tricky to pronounce) so plural form is "ce sont"
Pronunciation of "bottes" is confusing.