The lower bake element did not heat up

First I made sure it was in fact the lower bake element that was broken. I turned the oven on & noted the element did not glow red. I also used a laser thermometer to verify the element was at "room temperature" for the room it was in (the oven - about 200 degrees, given what the upper bake element was contributing.)
And close visual inspection showed that a section of te bake element had melted thru where something had recently spilled onto it.
Swapping it out was easy - turn off the electrical breaker controlling the oven, unscrew the bake element, disconnect the electrical contacts to it (which required pliers, since they had been on a Looong time, and a little care to not use the pliers too hard & thus break the wires or contacts), then reverse the process to install the new element.

It works great now.