You know the floor mats they put at the entrances to shops and big offices? Get friendly with the people that swap them out
They are usually rented (despite often having the shop or office logo on them) so if the contract is lost the owners have a load of mats with an ex-customers logo on them. Likewise if the company changes their logo there are a load of useless mats kicking around. I've had loads from a guy in the car club who works in the industry - free as they would otherwise go in a skip, they usually end up distributed around the family or friends but I've got three or four in the garage. Comfy to lie on, waterproof if the floor isn't dry and if you do manage to get them oily throw them out on the drive, dribble some fairy liquid on them and attack with a hose and a floor brush. OK they aren't mega padded but they are big and if you're working outside they won't blow away.
I just use an old boot liner. Added bonus the size of it means I don't have to keep moving it about and the lip keeps all the bolts, tools and oils from straying over the driveway. Wipe clean afterwards and doesn't soak up water when it starts raining whilst in the middle of the job
They were on special recently, £19 and came with a free kneeling pad.
There is just something about them, the material they use feels really nice. I've still got my old one that I bought probaby 18 years a go but I did buy a new one on the special.
When the kids were really small I bought a couple of mats for under the garden swing from a boot sale, they are around 6' x 3' and 1" thick. The kids are now 31 and 33 but I still have and use them regularly like this afternoon changing a wishbone (in the drive)
They came without a warranty but I wonder if the Snap-on's will last that long
For working on the floor on cars - you don't need a mat - they just get so dirty - absorb everything. When you start kneeling on them - your knees look black every night you have a bath.
You need sheets of - 2ft x 4ft x 10mm plywood - varnished or danish oil on the upper face only.
A couple of these will keep you off a wet floor - you can wipe water off them as it drips from a car.
If you have a spillage - you can wipe oil fuel and antifreeze off them. If you vanish them - the waste oil does not soak into the upper surface.
You can slide about on them.
If you end up working on shingle - you can lie them in sets about under a car - so when you drop something you can find it.
I had a van full of plywood - 3ft x 18" x 18mm for trolley jacks.
I used to buy - 8x4 sheets of 10mm - cut them into four to make sets of crawling boards. About this time my Father was into woodwork routing - he used to put a radius on the corners and edges (which does stop them splintering).
I only ever had really tiny "gardening type" kneeling pads - and used try my best to keep them away from waste oil - because once they got in on them you had to throw them away.
I soon gave up with rubber/foam mats and silly padded crawling boards with wheels.
When you get really into it - and have loads of 2x4 sheets of 10mm plywood - you can drill a 10mm hole in each corner - then with a few cable ties - you can use them for MIG welding - windbreaks outside.
Nothing worse than working on shingle or leaving oily patches/dents on peoples driveways.
Plenty of vanished sheet plywood wood is what you need....