Easy place is how the Arilou refer to one of ten specific parts of space, and possibly time. When you meet the Arilou in HyperSpace or TrueSpace they may note that "This place is an easy place". Whether this refers to this part of the galaxy, this "dimension", the Arilou's Sphere of Influence, or something else, is unknown.
The Arilou are exploring easy places to trap Nnngn. They note that at different times they explore different easy places. This may or may not refer to the three days a month that the naturally occuring QuasiSpace portal is open.