Here's how I made a heated build platform. It uses copperclad prototype PCB boards that are normally used to etch homemade PCBs. This material works very nicely because the thin layer of copper (35um) works as a heat distributer.

In the Netherlands it is quite hard to obtain insulated nichrome wire so I used Isachrom 60 resistor wire (which is 3.5 Euros for 10m)