There are several good plans available for constructing your own osprey nest platform.
A few key features:
Platform design recommended by the International Osprey Foundation. OspreyWatch nest 1156
Available plans:
Nest constructed as part of a class project. OspreyWatch Nest 488
V platform design recommended by the State of New Jersey. OspreyWatch nest 820
V platform design recommended by the State of New Jersey. OspreyWatch nest 389
Basic square platform with side perch. OspreyWatch nest 461
Wood pallets were used as the base of this nest platform. OspreyWatch nest 206
A plastic dish with drain holes is frequently used in Florida. OspreyWatch Nest 176