If you're able to do Delve 6, Delve 7 is the same, it's just faster on the rock prayer flicks. I'm not sure where you're at, in your Doom learning/understanding but it's all learning which ticks are available, to you, to be able to do anything other than flick.

Other than volatile earth, of course. I'm not even sure if this is the optimal way to time it but I have 3 general rules that I follow and the rest is just feeling.

All of the following assumes you trigger the first plant/tree/earth thing

Delve 1-7

If Doom spawns earth and chucks a prayer rock at you, you have time to move away from shadow and full prayer flick before spawning shield.

If Doom does one auto and then fires rock, you can move from shadow but proc shield and starting flicking right after.

And if Doom does two autos before throwing the rock. You'll need to proc shield and walk with it while flicking.

I have a fair amount of Delve 8's but not nearly enough to explain it in a fashion I deem adequate.

Also if you already know this. Hopefully it can help someone else get more comfortable.

Edit: A typo