In response to a question on our very first challenge regarding the 'rules' of One-Layer, Susan replied with the following:
I've always been a purist as far as this challenge goes. It is a challenge based on the following question: What can we accomplish with one piece of folded card stock, some ink or paint, and maybe a bit of embellishment?
Turns out, quite a lot of beautiful cards have been made with just the basics!
For our purposes on the OLS challenge, patterned paper is NOT allowed at all...strips or squares of it definitely constitute another layer of paper. Washi works essentially like patterned paper...it just adheres itself. So it's not allowed either.
As for larger, thicker embellishments, as long as they work on a one-layer CAS card, they are technically allowed but vigorously discouraged. Thickers walk the razor's edge, although the alphabet Thickers might work quite nicely on a very CAS card.
I can foresee challenge topics that push the edges of these very strict limits...say, for instance, a challenge that allows a single, very simple inchie on cards, or a challenge that allows a single strip of washi or patterned paper. But those challenges would definitely be the exceptions and not the rules.
We at the One-Layer Simplicity Challenge encourage participants to focus on the basics of card stock, ink/paint, and very little else to make beautiful art. People are often surprised at how hard that is (especially when they are used to making highly embellished cards!) and people are also surprised at how satisfying and FUN the process of making a clean, minimalist card can be.