Without slips or mistakes.
If something is slipless, it is usually good because it means there are no errors or problems.
Examples:
Her performance was slipless; she didn't make any mistakes.
The slipless document was perfect and had no errors.
He completed the puzzle in a slipless manner.
The slipless plan worked perfectly.
The slipless machine never makes mistakes.
The slipless journey was smooth and without any problems.