  The experimental realization of 2D Bose gases with a tunable interaction
strength is an important challenge for the study of ultracold quantum matter.
Here we report on the realization of an optical accordion creating a lattice
potential with a spacing that can be dynamically tuned between 11$\,\mu$m and
2$\,\mu$m. We show that we can load ultracold $^{87}$Rb atoms into a single
node of this optical lattice in the large spacing configuration and then
decrease nearly adiabatically the spacing to reach a strong harmonic
confinement with frequencies larger than $\omega_z/2\pi=10\,$kHz. Atoms are
trapped in an additional flat-bottom in-plane potential that is shaped with a
high resolution. By combining these tools we create custom-shaped uniform 2D
Bose gases with tunable confinement along the transverse direction and hence
with a tunable interaction strength.
