Trolls don't reproduce sexually, instead, a new troll baby is born when pieces of two or more trolls regenerate into each other. A ritual with troll parents might each cut off their own hand and link them together to grow. Their missing hands eventually grow back, but the severed hands form new life.
When a troll dies, it's dead. Or at least, the person that troll was is gone and treated as such. But the remains can be used to create new trolls, and might even spring up new life on their own in the right conditions.
I imagine trolls can look wildly different depending on a number of things like how much material was used to make them, which parts, where they grew up, maybe even what they eat. And some random mutations for good measure. A troll family might look nothing like each other, might not even be similar sizes, despite being directly related.
New troll lore: Trolls eat things that have rotted, decayed, or spoiled. They can eat fresh food, it won't kill them, but they don't get any nutritional value from it. They still practice agriculture, there's just a major composting stage involved in the process.
This has also led to the unpleasant stereotype that trolls just eat trash. That, on top of how frightening they can look sometimes, and how they might walk around missing large, freshly removed chunks of their bodies, has all led to them not having a great reputation. People are even afraid of them sometimes.