First, let me be clear, I'm not a real Doctor.
But I do hate to let work shoes go that have some life left in them. These are some tough shoes, no damage to the uppers, and still some tread left on the bottom. It is just that the insoles had rotted and would bunch up under my socks. So it was time for a fix.
Step 1: Gather Materials
So you could buy those fancy insoles from that other shoe Doctor. But if you keep your eyes open the materials are out there for free, or almost free. The play mat and old leather are from the Goodwill "Dollar Store" where they dump the junk and you pay by the pound. Kids play mats are thinner than the workshop mats, but whatever fits for you.
Step 2: Cut Out the Parts
If you are lucky there is enough of the old insole to draw around. You might as well make a nice pattern that smells nicer than your old insoles, and you can use it again next time. So trace the shapes on to the mat and the leather, remember to make rights, and lefts.
Step 3: Finished Parts
So you have the parts cut out and are almost finished. You could glue them together with contact cement, or use them as they are.
Step 4: Stuff the Parts Into Your Shoes
Now stuff the parts into your shoes. They may need a trim to fit nicely, if so edit your pattern for next time.
Step 5: New Life for Old Shoes
So there you have it, new comfortable insoles for your shoes at almost no cost.
Have fun, Carl.