There are two approaches to the Plone theme issue:
- Designing a theme from scratch
- Porting an existing HTML template
Ideally the right candidate is someone with a good deal of knowledge on the frontend side of things. The type of person who is studying at university after doing some other graphics/computer career. Perhaps having more experience than solely "leaning" on a framework like bootstrap/foundation/materialize. In other words, starting the project with more than a year of design experience is a huge advantage.
I don't know if 2 - 3 months is enough time to learn design skills and implement enough and deliver a reasonable theme. I've outlined what I think are the requirements for a minimum theme in a previous post (see: Defining a Minimum Viable Plone Theme Standard (A proposal))
What you'll need to learn
Regardless of which approach you take you'll need to learn:
- Diazo and probably a bit of XSLT (there are enough examples now in the wild, plus a mentor could help to curate the ones)
- What is needed for a complete theme (see link minimum viable Plone theme mentioned above)
Preferred Previous Experience
Depending on which approach I think it would be preferable if you know the following BEFORE the start of GSoC in April/May.
Designing a Theme from Scratch: What you need to know
Designing a Plone theme from scratch requires the following prerequisites:
- You already have strong frontend (CSS/HTML/JS) skills and are up to date with principles of responsive design
- You have a strong understanding of both the elements and principles of design
- Basic (not super) coding skill, enough to help yourself
Porting an existing HTML template: What you need to know
If you're porting a theme you still need to have a good understanding of frontend skills but you'll probably be able to get away with less design experience.