You can take a draft from Model Standing Orders, modify it a little here and there (organization-specific changes), and use the same after certification of standing orders.
There was an interesting case where about 90 misconducts were listed, and the 90 did not include knitting while on duty. Two ladies were found knitting sweaters. On the charge sheet, they argued that it is not a misconduct under the standing orders. They were reinstated in their job. The moral of the story is that there should be enough room to prevent the misuse of standing orders.
All the best.