There may be a better way but I've done this by creating a button that is invisible and the size of the kanban card.

Kanban View Definition - important items to note is the use of pointer-events: none (this disables the normal click) on the main div and then pointer-events:auto (this re-enables click events) on the button.

<templates> 
    <t t-name="kanban-box"> 
    <div class="o_kanban_record" style="pointer-events: none;"> 
        <button style="pointer-events:auto; position:absolute; width:100%; height:100%; background:none; border:none;" title="open" type="object" name="open_record"/>

Kanban Record Model Definition - as per normal kanban object buttons:

@api.multi 
def open_record(self): 
    return {
        'type': 'ir.actions.act_window', 
        'res_model': 'res.model', 
        'name': 'Record name', 
        'view_type': 'form', 
        'view_mode': 'form', 
        'res_id': self.id, 
        'target': 'current', 
    }