I am not sure if there are really any secrets other than just being patient and riding them and it will eventually even out. The smoother the concrete, the more noticeable the flat spot is so it my be less annoying to just skate street spots for while until it has smoothed out a bit. The double-edged sword of the STFs being a really hard wheel that doesn't wear very fast is that it may take a while to ride the flat-spot out. You could contact Bones about it but, depending on how much you skate, you could probably have the flat-spot ridden out faster than dealing with getting a new set of wheels.
From the Bones website...
All BONES WHEELS manufactured products are warranted against manufacturing defects for the useful life of the product. If you feel your skateboard wheels, bushings, or other BONES WHEELS products were defective, you may send it back to us, freight prepaid. We will inspect it and let you know of our findings. If we decide your returned product was defective or failed to give reasonable service, we will replace that product with a similar, available product of the same or better quality and pay for the shipping back to you. You can send in multiple products to be inspected for your return. We will evaluate each product separate and will replace any and all products found to be defective.
If our experienced inspector decides your product was not defective, you will be informed and asked if you want your product sent back to you, or destroyed. For those not receiving a replacement product, you will be given the opportunity to buy another one at a discounted rate from us.