The objective is to process at least 100,000 tonnes of ore in order to estimate the diamond grade and average value.
The process, it is hoped, will generate an internal resource statement as well as valuable cash flow, with the first sales expected to begin in fourth quarter.
The project is in the heart of the Aredor district, an area renowned for producing high value stones.
Stellar said waste stripping and ore extraction for stockpiling has already commenced.
Chief executive Karl Smithson added: "I am delighted that our team at Baoulé is continuing to deliver on schedule resulting in our processing plant now being fully constructed ahead of imminent trial mining.
“Commissioning is underway to establish the optimal operating parameters for the plant, after which the first kimberlite ore will be processed.
“Our objective is to process a very large sample which will not only establish the diamond grades and values with high levels of confidence, but also determine the presence of any large stones for which the Aredor region of Guinea is world renowned.
“During this process any diamonds produced from trial mining will be sold in order to generate cash flow for the company.”