There is a bug with the post editor. Images pasted from other websites from your clipboard will automatically use the [img] tag instead of uploading a copy as an attachment. Please manually save the image, upload it to the site, and then insert it as a thumbnail instead if you experience this.
The [img] should essentially never be used outside of chat. It does not save disk space on the server because we use an image proxy to protect your IP address and to ensure people do not rely on bad third party services like Imgur for image hosting. I hope to have a fix from XF soon.
IME, if you have a pizza pan, the best way to do it is take the pan out of the oven, pre-heat the oven to 350, then put the pizza on the pan and stick it in the oven for 5 minutes or so (you can usually tell how things are going by the smell.) The only reason I'm being so pedantic about the pan is if you let it get hot during pre-heating, it'll dry out the bottom of the pizza really fast.
Toaster oven is my favorite, but I put a tin foil layer under the pizza so it mostly gets heated from the top and the crust doesn't burn. Most of the time I get pizza I find it a tad under-cooked, so I often like it better the second day this way.
Put a dish of water in your hot oven until its steaming then put the slice in on a rack or something so the steam can circulate around it. Leave it in until the cheese has remelted and the crust should still be crispy or soft depending on the bread type.