How to create a perfectly measured Rounded Border?

Steps:

Assumed Specifications

Design's Size – 150 cm x 200 cm

Border Size – 10 cm

• Create a new file,  according to the specifications given above (150 x 200 cm).
• Go to CarpeTools >> Modify >> Quick Shapes, select the shape type to Rounded Rectangle and Click on “OK”

• Again Create a new file and make sure that the size is 130 x 180 cm to make 10 cm border as mentioned in the above specifications.
• Fill the canvas with the different color.
• Now go to CarpeTools >> Modify >> Quick Shapes, select the shape type to Rounded Rectangle and Click on “OK”
• Select transparent color as the background color .
• Go to Image >> Canvas Size and change the canvas size to 150 x 200 cm, set the anchor point to Middle and click on "OK"

• Then select all the elements of canvas (Edit >> Select All) and copy it.
• Now again go to the main design file.
• Create a new layer and paste it in the new layer.