Easier than I thought. Here's an example of a button with various attributes calling a process.
<div>
<style scoped>
.button-launch{
background: rgb(69, 146, 214); /* Blue */
color: white;
border-radius: 4px;
text-shadow: 0 1px 1px rgba(0, 0, 0, 0.2);
width: 20em;
height: 4em;
}
</style>
<button class="button-launch" onclick="AwareApp.startProcess('LaunchQuestionnaireReference', 'Main', this, false)">Open Questionnaire</button>
</div>