slack.com remove left sidebar

remove-sidebar.css

/* hide the sidebar */
.client_channels_list_container {
    display: none;
}
#team_menu {
    display: none;
}
#col_channels_bg {
    display: none;
}
#col_channels {
    display: none;
}
#messages_container {
    margin-left: 0;
}
#messages-input-container {
    left: -160px;
}


/* move the favouites star over */
#channel_header .star {
    right: 50px;
    left: auto;
}

Updated from the original to handle changes in the Slack design (I think?)