Two things that helped us: 1) "activate" the diaper [0], they are tightly pressed for transport and have to unfold the fabric to soak well. 2) Make sure the side guards are up, tight fit around the legs and a short pull around it to adjust them and not have the guards folded under the seam also helps.

[0] https://cdn.shopify.com/s/files/1/0700/5519/8950/files/brief...