painless

painless
pain‧less /ˈpeɪnləs/ adjective1. causing no pain
   OPP  painful:
    a painless death
2. not difficult or unpleasant to do
   OPP  painful:
    The train is a quick and painless way to travel.
    The interview was relatively painless.
—painlessly adverb
     

THESAURUS

   ▪ easy not difficult to do, and not needing much effort: an easy task | The house was easy to find.
   ▪ simple easy and not complicated – used about things such as instructions and explanations, or about machines and systems: The system is relatively simple to operate. | a simple recipe for chocolate cake
   ▪ straightforward easy to understand or do, and unlikely to cause you any problems: a straightforward explanation | The calculation is fairly straightforward.
   ▪ user-friendly easy to use – used especially about computers or written information about how to do something: Their website is very user-friendly. | a user-friendly guide to owning a dog
   ▪ undemanding easy because it does not take a lot of effort: It was an undemanding role for someone of his experience.
   ▪ cushy /ˈkʊʃi/ informal a cushy job is easy to do and needs very little effort – often used when you are envious of the person who has it: It’s a pretty cushy job – all she has to do is drive a nice car around. | a cushy number (=a very easy job)
   ▪ mindless so easy that you can do it without thinking – used especially when it makes you feel bored: mindless tasks
   ▪ painless without any difficulties or problems – used especially when you expected something to be much worse: Finding the carhire place at the airport was relatively painless. | Thankfully, there's a wide selection of search tools to make the task relatively painless.
   ▪ be plain sailing British English, be smooth sailing American English to be easy and with no problems that you have to deal with: Things should be plain sailing from now on.