Yes, you can place sell orders anytime through your Mintos account. Like buy orders, sell orders are executed instantly when the exchange is open during trading hours.
If you place a sell order when the market is closed, it will be processed as soon as trading resumes. You'll always see the current market status and expected execution time when confirming your order.
Please note that while your sell order is executed once the market is open, receiving the cash in your account may take up to 3 business days.