After the initial felting in the bucket and tumble drying on high heat, I ran the clogs through a couple of loads of laundry. They were still too long and I could still discern the individual stitches.
Before any felting...
Now, after going through the two wash loads (with bulky, dark clothes) the stitch definition is almost completely gone.
Generally felting can shrink the item almost to half long-ways and by about a third in width.
The clogs are knit with a double sole. It makes them nice and 'squishy' and provides a better-wearing double thickness. I made sure not to have any knots on the soles and when I was stitching the centre sole seam closed, I used a fairly loose whip stitch that just butted the two edges together. There was no overlap creating a ridge.
They didn't turn out as fuzzy as several folks on Ravelry who had used the same yarn had said. That could be because I pre-felted in the bucket and loosened and washed away a lot of the wool fibres at that time. There was hardly any wool fibre on the dryer filter last night after the tumble drying.
I have enough yarn to make another pair a size or two smaller.