Answers for "bootstra flex start"

laravel clear cache

php artisan cache:clear
php artisan route:clear
php artisan config:clear 
php artisan view:clear

artisan cache clear

//Laravel 7 / 2021-01
php artisan cache:clear
php artisan route:clear
php artisan config:clear
php artisan optimize

bootstrap display flex

<div class="d-flex">I'm a flexbox container!</div>