Stick to Lean 6sigma basics. However, this is not an easy task if already lean culture is not established in your plant. Give more details about the plant you are planning to apply Lean 6 Sigma.

My learnings are:

• Lean is a continuos improvement journey; a journey with no end.
• Lean is a philosophy (an organizational "attitude") before being a set of tools.
• Lean tools complement with Theory of Constraints (drum-buffer-rope) and with Six Sigma. Each of the three serve a different purpose; start with TOC, next Lean, use Six Sigma as you go along... loop back to TOC.
• Lean is an organizational learning process. As a learning process, lean is interactive, incremental and recursive.
• The adoption of continuos improvement methodologies should be guided by the business strategy.

http://scm-institute.org/booksamples/PageOneOfChapter12.pdf

This link explains the concepts of lean and 6 sigma, i.e. lean sigma is very simple ways. However, before starting to embrace it, there must be an alignment for this approach across the organization, particularly at the top.

https://goleansixsigma.com/what-is-lean-six-sigma/

Value stream mapping the present state of an actual plastic recycling facility will enable you to identify where there is push, pull and where there are wastes. Likewise, it will become evident whether there is a balanced flow and where bottlenecks exist. This way, through the implementation of the lean principles of pull and kanban it will be possible to create a VSM of a future improved state which will be a more efficient system. Maintaining the importance of kaizen or constant improvements means that we try to constantly make improvements in production systems, in order to maintain competitiveness. 

The application of methodologies based on the continuous improvement of quality is valid to raise the performance of organizations and are the starting point for the application of other approaches such as Six Sigma, Lean Production and the development of innovation projects

First, decide if you will go for a only-Lean, only-SS or LSS approach (your title says Lean, but your question is about SS). Then, if you want to go for Lean, the very first step in a successful implementation is 5 S technique. Once you master 5S in your recycling plant, return here for more advice. Saludos!

Hi! I advise you to read a lot of journals related to your topic. 

It is easy if you follow the normal DMAIC process. It gives you a good guideline or a framework. First of all, you have to define what you are going to improve in terms of variation and what is your ideal measurement to identify the real root cause.