on seller hub, go into Seller dashboard, from there on left side column go to preferences, then on that page click "business policies," from their you should be able to add shipping policies. Start one for example priority mail if you think for instance you could ship the PFRE set your price for one & if , then you can add another service in the same shipping rule with Priority mail only not any flat rates and set a price & then add extra cost , it's always a guess to add the amount that you think would be enough to cover combined shipping on orders to cover your cost to the furthest locations and most expensive as well from you. After awhile of this happening if you come out short to these locations, you can go in and change the additional amount to try and get closer to the actual cost. There will be times though it will most likely charge a little extra to buyers who are closer to you. It's really hard to get the exact cost charged to each buyer due to different locations as you can know ahead of time what people are going to combine , so calculated shipping doesn't work but only for one item. I always try to factor in my ebay label cost of shipping plus the shipping fee's I get charged, I think I have it figured out at being 10.4%. This is why I don't charge the buyer what I pay for ebay labels, because then ebay tacks on the 10.4% in shipping fees. I'm already not making much profit so I can't afford to eat these fee's. Of course other buyers that offer lower shipping prices than me more than likely might get a sale before me, but I have to do what I have to to stay afloat. I do still make sale, granted maybe not as much if I had cheaper shipping but given the views I'm noticing on my items compared to years past I doubt it.