A hot bed is basically a trench filled with organic materials and capped into a mound with top soil. This method was very popular with the Victorians and is one of the most economical and rewarding ways to produce a good crop. You should expect high fertility for at least 4 years or until the mound flattens. As the organic material in the mound rots in will increase the temperature (hence the term 'hot bed'). This will induce an faster growing and an early crop as well as a long term improvement in general soil structure.
Dig a trench 12-14 inches deep. The trench can be as long as you wish, but ensure that you can easily reach all parts with having to walk and compress the soil.

Your hot bed is ready for planting. Good luck.