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Place 2 walls at the corners of the ore patch.
Take a new blueprint and select your 2 walls. Then, click on Export to string and copy the string into the textbox on the website.
Select all of the options you want, like the position of the train station, belts...
Turrets and walls can be useful if your ore patch is far from your base.
If your number of cargo wagons is 1, 2 or 4, you can skip this step.
Otherwise, you'll need to provide a balancer blueprint.
Now, you can click on Get Ore Outpost Blueprint. It will give you a string to use in Factorio, copy it.
If you want to save your settings for a other use, you can click on Get Settings URL. It will give you an URL. When you will load it, the website will set all of his settings as you selected them.