At CHIIR 2019, Berget and MacFarlane [4] pointed out the need for ethical methodologies when involving participants with dyslexia. In this paper, we further propose that a stance of ability based design and participatory design approaches can further involve, engage and support people with intellectual disability in interactive information retrieval (IIR) research. Through a case study with an accessible prototype designed to access instructional videos, we demonstrate how an approach building on participant's interests and providing them support as part of the study design leads to ecologically valid observations. The accessible prototype makes use of images as prompts and query support, and includes social aspects. Our observations confirm that users with intellectual disability favour a visual approach to information access and interaction. The contributions of this work are primarily 1) a 2 step approach with supported participatory design approaches involving early prototypes 2) a case study of this approach to investigate information access interfaces with people with intellectual disability and 3) a reflection on the case study and applicability of the method in IIR evaluation.