If you are unable to get slice to work, you can do something like this.
[X2,Y2,Z2] = sphere(100);
X = X2 + 0.5;
Y = Y2 + 0.2;
Z = Z2*0.5 + 0.1;
surf(X,Y,Z)
hold on
surf(X2,Y2,Z2)
hold off
p = gca;
p.View = [0,90];
Zslice = 0.2;
p.ZLim = [Zslice-0.005,Zslice+0.005];
