Quilters hold fabric in place with freezer paper while piecing their blocks; it’s basically plastic-coated paper that gets tacky at ordinary clothes iron temperatures.
It’s useful in the shop, too. Cut a length of freezer paper into small pages, pad them plastic-side-up atop a sheet of cardboard, and you get a great place to mix small amounts of epoxy:
Let the pad stay next to whatever you’re epoxying (like, say, the lathe tailstock ways), then test the leftover epoxy for hardness… rather than messing up the joint you so laboriously created by moving the parts an hour too soon.
Works for me, anyhow. Highly recommended!
The Smell of Molten Projects in the Morning 
Looks like a good option. I use the little paper cups commonly used for ketchup (yes I bought them ;-) and popsicle sticks. I also keep the residue in the mixing cup to test the progress of the epoxy.
Back when I ate far too many raisins, I had a good supply of plastic lids. A huge box of those wooden sticks Came With The House™ and might run out within the decade.
I like mixing epoxy on a flat surface, because it has no corners to hide in. The tradeoff seems to be occasionally dragging a sleeve through the puddle. [grumble]
My favorite was small yogurt lids, but the plastic ones have been eliminated To Save The Earth. I usually scrounge a bigger lid from something, or a bit of blister pack plastic.
Old business cards work well by me. I have many boxes accumulated over the years.
I used to use wood sticks/toothpicks to mix, but I found an assortment of chrome-plated spatulas (spatulae??) at a hobby outlet and have been using one of them to do my mixing. The key is to clean the spatula before the epoxy has cured. So far, I’ve remembered to do that.
I’m also curious if you have experimented with heat-curing any of your JB Weld operations? I’ve been doing this for some time using my kitchen (electric) oven, and it is a real time-saver. You get the long work time of the standard JB Weld mix, and a cure time of 1-2 hours. Works great for those projects that can be placed in the oven space. I’ll dial the oven to 175F and wait until the element shuts off. Then, I turn off the oven and remove the knob (this is my signal to others that the oven is in use…helps prevent unfortunate results should someone come along and want to actually cook food in the oven). The workpiece goes in, and I wait for the smash to cool to room temp (about an hour and a half, give or take). The viscosity of the JB drops initially, so one must be conscious of this when positioning the workpiece, but I’ve not found this to be particularly bothersome.
Ah, yes. Not cleaning the little screwdriver after maneuvering epoxy into a tight space: I hate when that happens. You’d think I’d know better by now. [mutter]
I sometimes aim a heater / lamp at whatever I’ve just epoxied together, but I usually just wait for tomorrow to arrive. One exception, a pinhole leak in a furnace heat exchanger, called for both a quick cure and high temperature operation; my 100 W work light / heat source liquified the epoxy exactly as you describe. Didn’t matter, but I should’a known better about that, too.
Obviously not an issue for this particular job, but in critical work keep in mind epoxy manufacturers warn against using waxed paper cups for mixing because the wax can interfere with the bond. The same would apply to waxed paper pads, I’d think. Otherwise it’s a nice hack! I’m tempted to try it with some heavy-duty polyethylene drop cloth.
Hadn’t thought of that; thanks for the tip.
The box proclaims “Plastic Coated” and it feels like polyethylene, but they’re not forthcoming about the details. It’s definitely different than waxed paper, which I confess I’ve used on some occasions. Now I know better!
You can get dental mixing pads for not much money. They come in several varieties & sizes of impervious paper, bound on 3 edges.
< https://www.net32.com/ec/mixing-pads-slabs-materials-l-513-595 >
The reviews seem, ah, mixed; some folks say whatever they’re mixing oozes through the plastic coating. They definitely do a neater job making the pads, though.
We have a cleaning appointment in a few weeks; maybe I can mooch a few sheets to try out.
Thanks for the suggestion!