the unit of measure for the "Whole Pecan Pie" product would likely be "Each" or "Unit", since you are selling the entire pie as one unit. The unit of measure for the "Pecan Pie Slice" product could be "Slice" or "Pieces", since you are selling individual slices of the pie.

When you create the BOM for the "Whole Pecan Pie", you will need to specify the unit of measure for each component, including the "Pecan Pie Slice". The quantity of 8 slices should be specified in the unit of measure for "Pecan Pie Slice" (e.g 8 slices).

You can also create a conversion between the two units of measure, so that you can easily track how many slices are in a pie and how many pies are in a slice. This will also help you to calculate the cost of each slice based on the cost of the whole pie.

It's also worth noting that Odoo allows you to set up multiple unit of measure for each product, if you want to sell the product in different unit of measure, for example, you can sell the pie by weight or by the inch, and it will automatically convert the price and stock accordingly.

Please note that this is just an example, and the exact code may vary depending on the specific version of Odoo and the customizations that have been made to the system.