Before starting there may be a few factors you may want to consider;
What type of decking sub-frame would be most suitable for your project? Do you need to apply for planning permission for your project? Have you taken into consideration the finished height of your deck?
Whether you are sourcing your own joiner/carpenter or are performing a self build please ensure to follow the installation guidelines available for the most reliable and efficient installation. Failure to lay joist work at 400mm centres or leave gaps end to end for expansion and contraction will limit your warranty.