From where do I access the lower oven element on a Amana ACF4215A

See service manual or contact manufacturer.

You need a 1/4 or 1/16 mm. to take it out, they always have a simgle plug.

You should check your Hi Limit thermal switch part#74008715 you will have to remove the oven from the wall to access this part.
http://www.on-timeappliance.com/ovenrepair.html

First check the temperature probe if that checks out good the problem is the bake element is failing. Here is a couple links on checking and replacing these parts
http://appliancehelponline.com/oventempprobe.html
http://appliancehelponline.com/ovenelementvideo.html

it could either be a hot spot in the element where it can no longer pass all the current needed for proper operation in heating(look for a discolored spot on it,it may be whitish and dimpled from heat) or secondly,it could be the oven thermocouple located on the inside top of the oven cavity

Try a few drops of vegetable oil on the lower pan of the oven, and turn it on. If you do not get smoke during pre-heat, chances are your lower element is not working properly. If you DO get copious amounts of smoke off the pan, the problem could be with the temperature sensor.

If your lower element is not functioning, and if your broil function works just fine, the problem may be isolated to the relay control board. (relay K4 controls half of the 240V required to run the Bake element correctly)

Your "Bake" element may not be working properly. It's the one in the bottom of the oven. Place a couple drops of vegetable oil on the bottom pan, and turn the oven on. During pre-heat, you should start to see those oil drops generate some smoke, IF the lower element is working properly. If it isn't - voila'.!! Problem is with the lower element / associated circuit.

Replace your bake element. Common problem.

You need to access through the back to get to the connection on the back of the element. Be sure to unplug the machine!

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

In most ovens, both elements are used during the warmup phase even when used for baking and after the set-temperature is reached, the lower element keeps it stable.
You should be able to detect which one is not working with your bare hand. Set the baking temperature for 250-300 degrees, leaving the oven door open. Hold your hand at different heights in the oven and you should be able to sense which element is working and which isn't within a couple of minutes.
If you still aren't certain, then try using the broil element only. If it is heating, then it's obviously OK and that would point to the bake (lower) element by default.
A final check could be done with an open door and hovering with your hand over the lower element; no heat = defective.