Infusionsoft Oder forms and upsell forms on Custom Domain


What are some of the best ways available for self-hosting infusionsoft order forms?

I know that it can be achieved via Legacy Order Form. Does someone have step by step tutorial on how to set one up for both the initial and upsell legacy order forms on a self-hosted domain? Do we need to use IS php SDK for that or do we just need to embed legacy orders forms on a Secure Page?

Thanks in advance and I am looking forward to the community to share their best practices on how they are achieving this goal in 2018

You can use FormLift for a pre built and tested solution.

Thanks Adrian. Looking for a custom solution rather than third party plugins.