Can I make an extension cord with left over house wiring?

I need an extension cord now and I have pretty much all I need at hand, but I am unsure if it will work.

I have 12 meters of 12 guage house wiring, and I was planning on cutting it for a 4 meter extension cord (neutral, live and ground), and I already have the male and female plugs.

However the wires would be just dangling (not like a regular extension cord with all the strands in a pvc kaxhety) is that unsafe?

I was thinking on adding some conduit but then the plugs may not fit.