How do I attach the legs to a 500-lb oven and set it upright without using a forklift?

We recently bought a 500-lb oven which came with the four legs unattached. We can turn the oven on its side and screw in the legs but then how do we set it upright with just me and two other small guys and no forklift (heavy lifter)? Turning it after attaching the legs may break the legs supporting the weight as it is turned.