configure Holiday based on different feild

Need to Configure Holiday based on "Assignment location" field which is DFF feild ( which we have created for our internal purpose). Customer wants to assign the public holidays based on Assignment location but not on the base location.

We have a requirement from our customer where we need to map public holiday against location where facility, in reality, does not exist. Hence, We can not create base location in Fusion. However, We have a different location which points to same location master.
Need to configure the public holiday against that field. please let us how to achieve this ?

Please help me to how to achieve this.