The antonyms for the word "more foundationless" can refer to things that are more stable or secure. Words such as "founded," "grounded," "stable," and "rooted" are all antonyms that convey a sense of stability and support. When something is "founded," it is built on a solid foundation, and when something is "grounded," it is firmly established on solid ground. Similarly, "stable" and "rooted" suggest that something is well-established and unlikely to collapse or waver. By using antonyms for "more foundationless," one can convey the opposite idea of something that is strong, secure, and built to last.