What Kind of Glider?
They're all a bit different.
Anyway the modern glass ships generally have such powerful spoilers that you don't need to bother with sideslips.
In many you can simply pull full spoilers and point it at the chosen landing spot if you're high enough. The added airspeed adds drag. In such cases, you do need to maintain sufficient airspeed and perhaps reduce spoilers to half during roundout to avoid a heavy landing -- depends on the glider. The manual will tell you.
However many of the older two-seaters such as Blaniks don't have such powerful spoilers; so, sideslips can become necessary.