The easy way to resole shoes. It takes about 20 minutes.
Your shoes will be more comfortable than when they were new.
What a great way to start the new year!

I'll demonstrate by resoling a pair of Crocs using contact cement and foam from interlocking floormats.

WARNING:
Until you add tread, the new soles are almost as slippery on wet pavement as the worn-smooth crocs were.

Step 1: Flatten Your Soles

We'll be gluing a half inch or so of foam onto the bottom of each shoe.
You might want to grind your soles flat with a beltsander or disk sander with the coarsest grit you can find. Instead of flat you could go nuts with amateur orthopedic theories.

My Crocs have worn down pretty flat so I'm going to skip the grinding.

Step 2: Trace Onto Sole Material

You can trace pretty tight, you'll be cutting around this line.

Step 3: Cut Out the Soles

Cut out the sole with a sharp knife or the tool of your choice.
Leave a bit extra around the edges.
An electric turkey knife is good for cutting soft foam.
This foam is about the same density as the croc foam.

Step 4: Contact Cement

This glue is amazing.
It's also good for causing headaches, brain damage, and explosions.
Use it somewhere with good ventilation and wear a mask with organic vapor cartridges.
Follow the directions. If you smell this stuff you're doing something wrong.

Step 5: Apply Glue

I leave the brush in the can so it lasts forever. I cut the brush handle short so it'll fit.
Paint it on the mating surfaces of the new and old shoes.
If it's glossy at first that's enough. If it runs that's too much.

DON'T PUT THEM TOGETHER YET. WAIT FOR IT TO DRY FIRST!
That's what the directions say, and that's how this stuff works.
If you stick them together wet they'll come apart later and pick up dirt etc.
When it has a matte look to it that's enough.
For a super strong joint I'll drive off all the naptha using ninja tricks before mating them.

Step 6: Sole Mates

Line them up very carefully before mating.
If they touch first you might have to rip something to get them apart.
Then squish them together to bring all surfaces fully into contact.

That dingus sitting on the glue can is a paint can opener. Paint stores give them away for free.
It's the right tool for opening paint cans, just like the name implies. If you use a screwdriver instead, there's a good chance you'll damage the lip and your glue will dry out in the can.

Step 7: RiverDance

Stomp around a bit and squish the surfaces together really well.
Enjoy the fine feeling you get from your new soles.

Step 8: Trim the Edges

Trim it like your shoe theory tells you. I like it pretty close.
Then squish the sole tight all around the edge with your thumbs.

Step 9: Finish Grind

If you want to sand your edges smooth, use a fresh coarse grit abrasive in the sander of your choice.
Use a light touch, some types of foam will roll and rip if you use too much pressure.

And that's it! Enjoy the cushiness of your immortal shoes!

When your new sole wears down past the tread and you want good traction again you can impress new tread in it with the edge of an iron.
Don't slip and fall.