Hi and Happy new year!
You don't say if he is totally dry or only in the daytime or his age so I'll give you a rough idea what I have done as a Nanny for a long time now.
I'm figuring that if totally dry and no longer in nappies or pull ups then this wouldn't be an issue and so I'll answer as if he is wearing a nappy for sleeps.
If his nappy is often dry after naps and sleep, taking away the poo issue then stop wearing them altogether.If he has been dry for a year in the daytime, then he should manage nightimes well.It may take a week or so but he'll be able to do it.
Pull ups for some children are not a great idea as they still psychologically think of them as a nappy and so don't try to be dry.
Have a special chart...a sticker for each poo in the toilet... Take images of his favourite character from TV or book off the computer and spend time with him making his own little chart...sticking all the characters on a piece of paper. If you have a laminator, then laminate it so it is reusable..if not, use as it is. Stick it to the toliet wall or door etc...and buy or make some fab stickers to have if he poos successfully.
If he has that regular time that you have mentioned, you are lucky! Sit him on the toilet at those times for a few minutes to try. If he doesn't manage, fine but watch him like a hawk and if he starts to poo in his nappy, whisk it off and back on the loo.
Empty all poos into the loo with him and let him flush it away.Don't show any disgust at this...it is just a poo and that is where it belongs is the message you want him to learn.
Above all it is being patient and consistant that works. Deviate from your routine even just once and he will seize on that and you will need to start all over again.
Last thought...make sure the loo is comfy and a nice place to be. Buy a soft toilet seat rather than the hard thin plastic ones or buy a toilet seat that has the mini seat incorporated in it too. My friend has that and it is terrific.
Keep his diet good and make sure he has plenty of fluids. Don't panic too much if he doesn't open his bowels for a couple of days but naturally keep an eye on the situation. With a balanced diet and lots to drink, it'll be hard for him to become too constipated.
Lots of luck !!
xxKaren