jQuery.ajax( {
 url: Slug_API_Settings.root + 'wp/v2/users/',
 method: 'POST',
 beforeSend: function ( xhr ) {
 xhr.setRequestHeader( 'X-WP-Nonce', Slug_API_Settings.nonce );
 },
 data:{
     email: 'someone@somewhere.net',
     username: 'someone',
     password: Math.random().toString(36).substring(7)
 }
} ).done( function ( response ) {
 console.log( response );
} )