Baking with oven without bottom heating element
For things that can be baked for a short period of time, you can partially compensate by adding a baking stone in the bottom of the oven, then sufficiently preheating the oven.

The stone will release its heat, resulting in there being some additional heat coming from the bottom of the oven.

For pizzas, you can move the stone closer to the top element, so that you can get it very hot, and then lay the pizza onto the stone, so that the bottom will cook from conduction, not just radiant heat.

If this still isn't enough for cooking a pizza, you can put the naked crust on the stone, let it cook until it's developed a bit of a crust on the top, flip it until you've browned the bottom, then remove it, top the pizza, and slide it back in (right side up).  

You can also just brown it and then flip and top it, but your pizza will seem strange, as the top is now the flat side of the crust ... and the toppings will be more likely to slide.