ᐅ Raised garden beds, plastering, and protecting the base against moisture—how to do it correctly?

Good morning everyone,

We have just finished our terrace with porcelain tiles on drainage concrete. Now we want to build raised beds next to the terrace using formwork blocks and then plaster them.

Since I have no experience with plastering, I started wondering about moisture issues.

The terrace slopes toward the future raised beds and then continues to the lawn. Despite the slope, some water will likely collect in the corners.

My question is, what would be the proper construction or protection for the wall and plaster?

Should a 20cm (8 inches) waterproof slurry be applied to the formwork blocks—already covered and smoothed with reinforcing mesh—at the lower part, and then the finish coat of plaster be applied thinly while it is still damp? Or should the formwork blocks with the reinforcing mesh be fully finished with the finish coat, then treated with a protective base coat using a sealing paint or similar, followed by an overall coat in the desired color?

Can anyone provide tips or references on this? At my local building supply store, every employee has a different opinion, and I do not want to hire a mason or similar professional for this.

Best regards,
Fabian