No visible chalking. Or it's very gradual and minimal.
I find them (OR HAVEN'T!) in a few ways. Either observing a female digging or hanging around an area or by looking at areas that seem disturbed. I have red mulch on the ground and sometimes I can see that it has been dug up. Or an area that I have found eggs in previously. Such as inside of a broken very large pot and under a big construction pipe.
All of the 21 that I now have (27 found) have been found in the shade.
I suppose if you find them late, you wouldn't observe much chalking; thus making it a bit more challenging to tell if they did chalk. For me, chalking is easier to see when candling, although I try not to pick up the eggs. I was lucky enough to catch my female in the act of digging. I would think you would have seen some sign of an embryo by now. I've had infertile eggs (or failed eggs) darken inside before they split (gecko, bearded dragon, and tortoise), BUT I have also read reports that some "infertile eggs" have developed and hatched to the breeder's surprise.
I assume the two I have that are chalking will start developing soon. I think I saw an embryo the other day. If you would like pictures for comparison let me know. I know the internet provides some, although a small collection, for redfoots, but they are usually older posts. Ones you can't really interact with.
I find it amazing how well they put the substrate and mulch back. The eggs I accidentally found last week we're totally hidden. Top soil back then the mulch(orchid bark and Cyprus mulch) back on the top layer absolutely perfect.
Also Ed. Have you watched them dig the nest closely. They test the nest with there feet constantly. Are they checking for depth,nest size,warmth, humidity or making sure there is nothing hard that will break the eggs.
Do they know instinctively howmany eggs they are about to lay for nest size?
I've observed a wild red-eared slider laying in the same exact way. By time she's done, its looks more like the burrow of a beetle than a turtle nest. I am going devise a way to catch my girls in the act as I am not always there to follow them around. My redfoot laid in the same manor when I was able to observe her.
I also had the same question about clutch size. I've found a clutch of 6, and 3. Do they just dig the nest deeper as they age? Or do they know how big the clutch is?