Is there an alternative and less toxic way to clean an oven than using oven spray?
Using a bicarbonate of Soda paste is a good way to clean the oven and does not involve any nasty chemicals.

Also, as you need to clean the base of the oven, it can help if you remove the door if it is a drop down door.  This makes reaching inside much easier.  Most doors are designed to be removed easily.  Sometimes your manual will provide instructions on how to remove the door for cleaning.

Otherwise this video on removing oven door may help as it covers four different types of hinge.