Salem

(Decay?) Should I pave before building a split rail fence?

Will my fence decay? Is there any reason to pave the ground before I build walls on it?

Nope, all you need to stop decay is a claim. In fact, paving is something I would strongly advise against, because it makes you visible on the minimap. So do dirt tiles from levelling, sure, but those will decay back into normal terrain eventually, faster if you only flatten what you really have to.

OK, thanks. Is there a way to remove pavement?
And does paving have any effect on any buildings whatsoever?

Just dig on paved tiles to remove them. And pavement is just for aesthetics. Well, it also lets you build stuff on forest terrain (you can't normally build everything there), but so do dirt tiles you get from levelling.

Some buildings needs pavement to build on, e.g. a bread oven.

I've built mine on dirt just fine.