wp query - Custom Post Type - Display all, wrap in groups of 3

I've got a custom post type for staff members in a project I'm working on. I want to display all staff members in a slider, with groups of 3 rotating.

I need my listing to end up looking like this, repeating until all posts are wrapped in "slide" in groups of 3. The last instance of the slide can have only 1 or 2 posts in it if needed, that's no issue.

<div class="slide">
    <div class="employee">
        <div class="em-left">
            {post image}
        </div>
        <div class="em-right">
            <h2>{Title}</h2>
            <p><em>{Position}</em></p>
            <p class="performance"><span class="highlight">{Productivity}</span> productivity</p>
        </div>
    </div>
    <div class="employee">
        <div class="em-left">
            {post image}
        <div class="em-right">
            <h2>{title}</h2>
            <p><em>{position}</em></p>
            <p class="performance"><span class="highlight">{productivity}</span> productivity</p>
        </div>
    </div>
    <div class="employee">
        <div class="em-left">
            {post img}
        </div>
        <div class="em-right">
            <h2>{title}</h2>
            <p><em>{position}</em></p>
            <p class="performance"><span class="highlight">{productivity}</span> productivity</p>
        </div>
    </div>
</div>

My existing query, works great, outputs everything I need in the right format except the "slide" wrap.

<?php

               $args=array(
                    'post_type' => 'staff',
                    'post_status' => 'publish',
                    'orderby'   => 'menu_order',
                    'order'     => 'ASC',

                );

                $my_query = null;
                $my_query = new WP_Query($args);

                if( $my_query->have_posts() ) {

                $i = 1;
                while ($my_query->have_posts()) : $my_query->the_post();

                $id = get_the_ID();

                // grab custom fields
                rwmb_meta( $field_id);  

            ?>

            <?php 
                // grab photos
                $images = rwmb_meta( 'staff-photo','size=thumbnail' );
                $i = 1;
                if ( !empty( $images ) ) {
                    foreach ( $images as $image ) {
                        echo "<div class='employee'><div class='em-left'><img src='{$image['url']}' class='img-round'></a></div><div class='em-right'>";
                        if($i == 1) break;
                    }
                } else {
                    echo "<div class='employee'><div class='em-left'><img src='".get_bloginfo('template_url')."/images/placeholder.jpg' class='img-round'></a></div><div class='em-right'>";
                }

            ?>
                    <h2><?php the_title(); ?></h2>
                    <p><em><?php echo rwmb_meta( 'position' ); ?></em></p>
                    <p class="performance"><span class="highlight"><?php echo rwmb_meta( 'productivity' ); ?>%</span> productivity</p>

                </div><!-- em-right -->
            </div><!-- employee -->

            <?php  

                endwhile;
                }
                wp_reset_query();
            ?>