You can have the same or different customisation(s) in different positions (e.g. front and back) on the same product once you start the customisation process.
Adding your first customisation:
After adding your selected product(s) in your basket, click on 'customise and checkout' On the customisation page, simply click on the first '+' icon
Then follow the next steps, selecting only one position. You will be able to choose if you would like your customisation to be printed or embroidered, the position and its size. Once you have saved your customisation, you will see its preview on the garment.
Then you will need to click on the second "+" and either choose the same design at the same size to be in a different position or if you are creating a new design/size, select "create a new customisation" and follow the above process again.