1. A method for implementing an electronic design, comprising: using a processor to prototype the circuit design with a flexible model, wherein the flexible model replaces internal paths in the flexible model with filler content and retains interface logic portions of a netlist; and the flexible model comprises a clock tree abstraction for the circuit design, and propagating clock information by performing clock implementation for a top hierarchical level of the circuit design with at least the clock tree abstraction, without performing the clock implementation for hierarchical levels below the top level of the circuit design.