The default is to prepend the label, but you can change this by modifying the decorator's 'placement' option:
$this->getElement('isUserConsent')->getDecorator('label')->setOption('placement', 'append');
Edit: I never use this syntax for decorators but it should be something like this:
$this->addElement('checkbox', 'isUserConsent', array(
'options' => array(array('placement' => 'APPEND')),
'label' => 'Plz activate',
'validators' => array(
array('InArray', false, array(
'hay' => array(1),
'messages' => 'Please check the consent box'),
)
),
'decorators' => array(
'ViewHelper',
'Errors',
'Label' => array(
'placement' => 'append'
)
),
));