senta -set- gismu

x1 is a layer/stratum [shape/form] of x2 [material] within structure/continuum/composite x3.

See also flecu, nenri, rirxe, sepli, snuji, jbini, bitmu, sruri, serti.

In notes:

bitmu
x1 is a wall/fence separating x2 and x3 (unordered) of/in structure x4.
flecu
x1 is a current/flow/river of/in x2 flowing in direction to/towards x3 from direction/source x4.
jbini
x1 is between/among set of points/bounds/limits x2 (set)/amidst mass x2 in property x3 (ka).
nenri
x1 is in/inside/within x2; x1 is on the inside/interior of x2 [totally within the bounds of x2].
rirxe
x1 is a river of land mass x2, draining watershed x3 into x4/terminating at x4.
sepli
x1 is apart/separate from x2, separated by partition/wall/gap/interval/separating medium x3.
serti
x1 are stairs/stairway/steps for climbing structure x2 with steps x3.
snuji
x1 is a sandwich/layering [not restricted to food] of x2 sandwiched between x3.
sruri
x1 encircles/encloses/is surrounding x2 in direction(s)/dimension(s)/plane x3.
plinybinsenta
x1=s1 is a mantle of x2=s2 [material] within planet x3=p1=s3
tersetcka
s3 is a bunk bed with bunks/rows s1=c1 that are made from material s2=c2 and are for holding/supporting c3.