Toddler throwing/slapping

[IrishMamaMia]

My DS is 21 months and recently we are going through a phase where he throws things for entertainment, toys, food etc. He can get a bit slappy too when tired.
I'm finding dealing with it stressful. I generally say :We don't throw things, or 'Gentle' and 'Kind hands' and try to be positive but I have no idea if the message is getting through.
Whenever we are at a toddler group I feel really worried that he might hurt another child to a point where I feel distressed.
Generally his behaviour is okay outside of this communication is a bit difficult, he seems to understand but doesn't have many words (have brought him to see a local speech and language therapist and have some strategies from that)
Any tested ideas for the throwing and slapping ?

Have a 23 month old; I feel your pain. I watched one of the nursery workers in action with DS a couple of days ago. He did a first slap; she responded 'ah, you want to high five?' And they did. He laughed, then moved on to the next activity.

Young children get more cues from faces than from words, if you laugh, joke, smile be a twit, have fun they know you are happy with them. When you frown occasionally with a firm no or I don't like that it has more effect.

Try not to shout, be as calm as possible and try to get their indiscretions into perspective, they are learning, throwing is learning.
Discipline doesn't work when it stands alone, it has to be part of love.

When playing or just making a cup of tea describe what you are doing, say, "where's the tea bags," "oh there they are," any old rubbish.
No dummy, only when hurt or to go to sleep with.
Limit tv and hand held computers. Point to things and say the sound of the word that goes with it.

A word or letter is really just a shape, like the shape of an aeroplane.
Learning to read starts when they are very small, you point to a door or to a house and say the sound of the word that goes with them.

An actual house has a shape like the word.........house

Thank you both. Have taken discipline by love on board and the last 3 days have been very good indeed :)