Don't be a fool and don't start learning to play stun corv in siege. If you can't land stuns there is nothing to do there. Later, however, by all means. However in low elo it doesnt matter.

It's easier to land stuns after starting to fire at an enemy instead of using projection right away. You will learn to insta-stun after practice.

Corv is very good in 1v1s with most champs, but he struggles with champions that can silence, cripple, or that have massive hp.

Corv has 2 stun reset cards. Unyielding discipline is the hardest of two because if you miss you're a sitting duck. This card triggers for each enemy hit so if you hit 2 enemies with stun It will be 5s reset (if max level) plus with max Chronos, It would be 7,4s off stun making stun cooldown 0.6s. This is the best reset card.

The priority targets card, however, is super easy to use and is very forgiving. Yes, you lose the ability to fully reset the cooldown of stun, but in situations where teleport is used for escaping the reset will still be granted after healing an ally no need to stun an enemy. This card is best used in heal and hybrid loadouts, I use it as an filler for most builds. Both cards can be combined for best performance.

Corv can stun through shields and deployable making him a counter for champs like Vivian, Fernando, Khan, Term, and many flanks have a hard time against a good stun corv. Also, stun is useful for canceling movement abilities like Raum's juggernaut.

Sometimes hitting directly with a stun is not the best option. For those who are behind cover throwing stun behind them and position yourself so the teleport would deal dmg.

Depending on build you are running the playstyle changes. Some build what doesn't benefit much from being near you team are usually played agressive but build with cards that benefit you for being next to teammates is better played more passive and healing allies.

There is an indicator when throwing projection. It shows where is it safe to teleport or will you fall to your death (unless you use ult to save yourself, sometimes teleporting like this is useful, the indicator turns red btw).

Don't forget to mark an ally and heal whenever you can whoever you can. Heals are heals. Managing heals when playing dmg is the hardest thing to learn.

For the most part u will be using ur ult to be more aggressive cuz stun is a good defence ability as it is. When u stun an enemy in ur ult he will (most of the times) die.

Small tips

Mark flanks, or whoever is carrying.

Use teleport a lot. Recomend to teleport to highground or near teamates,

Remember u can still deal dmg but not the priority.

When playing 2mark It's most of the time the best option to heal the allies who are marked because of reseted cooldown/more healing to the ally u want/and more self heal, however, healing some1 who doesn't have a mark allows to heal 3 allies (I think it's more heals in general when healing like this when using Shadow Tribinal card for sure but u won't always get the full value), marked allies might be far away so this is the only way of healing them.

For the most part u will be using ur ult as a defence ability or just shooting it on point. If u refire ur ult u will gain some charge back.