Your skill will be the "claim" of your presentation.
You may want to give us background about which claim you have chosen will be important for you in your plans.
You might want to define what you mean by the skill.
The product from your portfolio is the evidence.
The warrant is your explanation of how/why your product shows the skill. Be thorough in this explanation.
If you have defined the term for the skill, connect the product to your definition.
This will work both for the skills portfolio and the English portfolio.