There are few "honest" ways to get great Crema. The first one is Freshly Roasted Coffee in a tuned Espresso Machine. Of course that is also how you maximize the sweetness of high quality Arabica beans.
The quantity of Crema rapidly decreases as the roasted coffee ages. The taste is also greatly affected by the staling that begins to make itself noticeable within one week after roasting.
In the first two pictures the Arabica beans were roasted four days previously.
The crema to liquid coffee conversion starts towards the end of the brewing process it is not so fast that the client would be deprived of a significant amount of Crema.
Though it is possible for anyone to add Robusta beans it is less likely when a roaster is serving freshly roasted coffee, because their brew will naturally have the great indicator of freshness. After all, a local roaster does not have a long supply chain which requires months to complete the distribution process.
Do yourself a great "flavour" by sourcing beans from a local roaster or someone who can deliver them within 2-3 days from the roasting date.
The brew in this French Press was prepared two days after Roasting. It is also significant that the beans were ground with a blade type grinder which yields a coarser ground that yields impressive results but is inconvenient because water will have to be added and the particles take longer to decant. If the Plunger is pushed too quickly the Screen will plug and a hydraulic lock will occur.
A burr style grinder yields finer and more consistent results. The finer grounds will infuse more quickly and will decant reasonably quickly. The screen is then pushed down to prevent the grounds from being poured into the cup. The solids do not add to the pleasant experience.
Develop a personal coffee ceremony to consistently get great results. If the results are not the best then try one thing differently and note if it is better or worse.