The Apollo3 library does not support to act as a SPI slave (see ReadME on GitHub - sparkfun/Arduino_Apollo3: Arduino core to support the Apollo3 microcontroller from Ambiq Micro)
I gave it try sometime ago apollo3/Ios at master · paulvha/apollo3 · GitHub. But it all depends on whether your board-pins are available. Read the .odt that is part of that library for the experiences and limitations.