Hi Josh,

The design of ServiceNow's SLA Engines has always been based on either fields within the task table, or on a separate task_sla table with two main references in it; one points to the SLA Definition (contract_sla) and the other points to the associated Task (task or table extended off task).

Links how to attach sla for custom table which is not extending any base table

How to use an SLA on Custom Application (table not extending form task)

would help you better.