Your chances of having corners in your house which are truly 90 degrees are remote.
The hand mitre saw is fine for cutting corners but you may need to make something other than 45 degree cuts.
I don't think joiners mitre inside corners on skirtings. They have a wee trick where they just mitre the top part; but I don't see any posts saying how to do this yet; maybe they want to keep that a trade secret lol?
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