Basically, every so often someone updates the stock, the items appear on the Clearance page, and don't get removed until someone manually does so. So you could very well see the item because it was there today, yesterday, last week, who knows? You have to actually click on the item to see if there is one still available for sale.
Then you just sit there and keep reloading until your size appears.
It's a pain but the prices are pretty darn good.