I purchased a WT901 sensor, and for ease of use, I designed a base to hold it using clips. The base features magnet holes to accommodate four 8x3 magnets or two 10x5 magnets (for convenience).
After four tests, I initially created a shorter version, but the magnets interfered with the WT901's compass readings. I lengthened it to 150mm, but unfortunately, interference persists. Other measurements remain unaffected, so I'll make do.

0.2mm layer height, 2 walls; the strength is sufficient.