sefta -sfe- gismu

x1 is surface/face [bounded shape/form] of [higher-dimension] object x2, on side x3, edges x4.

Also x4 bounds. See also crane, flira, plita, bliku.

In notes:

bliku
x1 is a block [3-dimensional shape/form] of material x2, surfaces/sides x3.
crane
x1 is anterior/ahead/forward/(in/on) the front of x2 which faces/in-frame-of-reference x3.
flira
x1 is a/the face [head/body-part] of x2; (adjective:) x1 is facial.
plita
x1 is a plane [2-dimensional shape/form] defined by points x2 (set); x1 is flat/[smooth].
korsenta
s1=k1 is a cortex (outermost layer) of structure s3=k2.
roksfe
s1 is a rock face / rock surface of rock / mountain s2=r1 on side s3 with edges s4.
tumsfe
s1 is the ground of land s2=t1 at location t2.