Business Process Integration
The following figure gives you an overview of a possible make to order process.

There's usually a quotation phase involved in the make-to-order business process.
Variant configuration can be used within the quotation phase.
Order BOMs can be used for the make-to-order quotations to create a technically complete product structure, which can be used as the basis for product costing and pricing.
In addition to the processes in Sales and Distribution, material requirements planning and production also work with an availability check.
Material requirements can be planned only after the quotation has been converted to a sales order.
Subordinate assemblies, components, and raw materials may be preplanned and already available or not planned (direct production).
If the direct production method is used, collective orders may also be used to simplify the production and costing processes.
Finally, all related production orders are settled.
Process Overview
The following video gives you an overview of a possible sales process. A quotation and order is used.
Quotation

The quotation must be complete. Otherwise, you cannot create orders with reference to the quotation.
The quotation must not generate requirements. See the following slides for more information.
You can run pricing in a quotation. You can use the sales order costing function to do this.
You can also maintain order BOMs and order task lists in the quotation. You could then use them for sales order costing.
Sales order costing can run in either unit costing or product costing. In unit costing, you can use the result of product costing and other manually created costing elements.
Create Order
The following video explains the creation of a Sales Order based on a Quotation.