Design guides
Below are guides you can use as a basis to design 'over'.
The yellow border is the "bleed" or trim margin, which will be cut off. Place texts and objects that should not be cut too close to the red cutting line and preferably within the safe zone (green line).
Anything that should indeed be cut should be placed well over the cutting line, up to the outer edge of the bleed.
For the backside, note that the right part (the pink part) cannot be used as it is reserved for the address, postal service barcodes, and postage indication.