If it's of any use, the small spring is visible in both the picture for step 10 and the one for step 11. It's especially easy to understand it's placement once you've seen the spring and see the image for step 11.

This step was the only one I needed to complete it so once I understood which grooves were being spoken of - the one underneath the short blade for the legs of the small spring, and the groove on the cast piece located underneath the side where the large spring is fit or in other words in between the small blade and the cast piece right in the middle (it becomes pretty obvious once found) - finally placing that small piece became easy.

Thank you for the guide!