Copy ie. the crud generator templates from gii/generators/crud/templates
to your application app/templates/mycrud
.
Then define the templates in your config:
$config['modules']['gii'] = [
'class' => 'yii\gii\Module',
'generators' => [
'crud' => [
'class' => 'yii\gii\generators\crud\Generator',
'templates' => ['mycrud' => '@app/templates/mycrud']
]
]
];
Until the documentation is finished you may also have a look at my Gii extension how to create a custom generator and templates.