Explanation: The best place on the SLDS website for the designer to find accessible HTML and CSS used to create components along with implementation guidelines is the Component Blueprints1. Component Blueprints are framework-agnostic, accessible HTML and CSS that provide the basic structure and style for Lightning components1. The designer can use the Component Blueprints to create custom Lightning Web Components that are consistent with the Lightning Design System. Design Tokens (B) are not the best place to find HTML and CSS, as they are variables that store design attributes, such as colors, fonts, and spacing2. Development Tools © are not the best place to find implementation guidelines, as they are tools and resources that help developers build and test Lightning components, such as VS Code extensions, LWC recipes, and Playground3.