The growing need for personalization and device independence calls for effective ways of engineering adaptive Web applications. This requires formats, languages and structured process models that allow developers to design and express adaptation, but also appropriate authoring tools. Still, current Web authoring tools do not provide sufficient adaptation support. Recently, the AMACONT project introduced a component-based document format aiming at efficiently composing adaptive Web applications from reusable Web components. This paper focuses on the development of such applications and presents a visual authoring tool called AMACONTBuilder. Based on a structured authoring process it is shown how it can be utilized for effectively creating AMACONT applications.