Here are two matters to discuss with your patio builder.
Whether you want the patio to be raised or level with the ground
You'll need to have a chat about whether the patio builder should make this structure raised or level with your lawn. Each of these options comes with certain advantages and disadvantages. For example, a raised patio could be a great option if your lawn floods sometimes during the winter because if the patio is elevated, the water from the lawn won't seep onto it and damage the patio floor or the furniture in this area. Having the builder create a raised version of this structure is also a great way to make an obvious visual distinction between the lawn and the patio, without having to put up any wall around this structure's borders.
However, a raised patio is likely to cost more than one that is level with the ground, due to the extra materials the patio builder will have to use to create it. Furthermore, if anyone who will be using the patio is in a wheelchair, you might need to add a ramp, as well as steps, to the raised patio to enable this person to access the lawn around it. As such, if you're budget is small and your garden doesn't ever flood, the patio builder might recommend a level patio rather than a raised one.
What shape the patio should be
You'll also have to discuss what shape you want this structure to be. If, for example, your garden in which you'll be building the patio features a lot of curves, such as a circular water fountain, curved garden path stepping stones, and a circular fire pit, then the patio builder might suggest that you make the patio circular to so that it complements these other features.
Alternatively, if you have your eye on some beautiful patio furniture, you might want to choose a shape that mirrors this furniture set's shape. For instance, if the patio table you want to buy is an unusual, irregular shape, having the builder make a patio that also has an irregular shape might highlight this interesting aspect of the patio furniture.
If your garden has a very classic, neat and well-structured appearance, then the builder might recommend a traditional rectangular or square patio that reflects the garden's classic style. As an aside, a patio with this traditional shape could potentially be less expensive than a patio with a more unusual shape, due to the simpler design process and how quick and easy the construction process would be.
Reach out to a patio builder to discuss your needs.