This document explain customizing needed to implement without any development a N-step workflow using the "SLAPPROVER" attribute, to clarify the explanation the whole document is based on a fake business case described below.
Business Case: customer establishes that the SC will need to be approved by line managers depending on SC total value with the follow criteria:
User1 -> Approval Limit $0
Manager of Org Unit 3 -> Approval Limit $200
Manager of Org Unit 2 -> Approval Limit $500
Manager of Org Unit 1 -> Approval Limit $1000
Solution Detail
Step 1) Create Organizational Units in Organizational Plan

TIP: a purchasing group must be responsible for the root organizational unit.
Step 2) Complete SLAPPROVER attribute
This attribute indicates which user will approve in case of exceed the own approval limit. The value must be US+<USER ID OF APPROVER> Ex: USAPROB3 and is completed at Position level.
For this example the SLAPPROVER attribute was customized as shown below:

Step 3) Definition of Approval Limit Values
The Approval limit values could be defined at PFCG Role Level or at Position Level in "Extended Attributes" tab.
Definitions for the Sample:


In case you choose to maintain the approval limit at PFCG role, go to "Personalization" tab 
Step 4) Worklfow Configuration
TIP : Create a BRF Rule in order to run the right process schema.
SPRO->Cross Application Basic Settings -> Business Workflow-> Process Controlled Worklfow -> Define Process Level


Process Level Configuration

In case the system cannot determine the approver ( i.e Shopping Cart with ammount $2000 ) will run automatic approval.
Hope This Help !!
Celeste