Create a PDF file with the crop mark as you want it. Then use the watermark preset to place this 8 times around the PDF's trimbox.
Make sure to select the option to place the marks "outside" of the selected PDF box and then define an offset to push the marks away from the corner. You should be able to use a single PDF for all 8 marks.
Once you define that watermarks preset you can use it in all your workflows. It will be shared between workflows so any update to the preset will be reflected in all workflows that use that preset.
Can anyone suggest a suggest a solution to layer crop marks in FreeFlow? I am trying to acheive the crop marks normally produced from Indesign PDF export. The unique look I am seeking is to have a white crop mark of thicker weight, layered under a black crop mark of thinner weight. The reason I need this is so that the marks are visible when placed on any color bleed. Attached is a snip of what it would look like. Thanks in advance.