Hi there E.,
I have 5 children aged 21,17,14,10 and 6.
1 yr olds can be very testing but most of it is just play.For EG: a child who is in a highchair,pram or walker,may just accidently drop a rattle,spoon or such and we would pick it up and probably smile or give some kind of playful attention upon returning it to them.9 times out of ten,the child will then purposely throw the item just have the same interracton as the first time.Of course it can be quite fun,but after a while,it must stop,for whatever reason.When mine did this I would allow a couple of times,but then I would firmly say no.If they continued,I would ignore their actions,and after a few grizzles from them,I would remove them from the highchair etc.
I found this to also be the same with the face hitting.Say no and then put them down or if you are sitting,then just move.They soon get the idea that it is not as much fun lol.Distraction is also good.
I do realise this was longwinded but I just wanted to let you know that your child is not the only one.My face has been slapped quite a few times over the years lol.
All the best to you...I hope this helps.
C.