This is similar to the regular TPRS free write where students write for ten minutes and try to get as many words as they can, however there is a slight twist. The 1-3-10 free write is more like a scaffolded free write because students work their way up to writing for ten minutes. The first time, have students write for one minute (with or without a topic). After the one minute, they count up their words and write the total next to their work. The second time, have students write for three minutes. They should copy what they wrote before and then continue on and write more. While copying what they wrote the first time they can fix mistakes if they catch them, but they should not spend a lot of time editing their work. When the time is up, they count up their words and write the new total next to their work. The third time, have students write for ten minutes. Once again they should copy what they wrote before (without spending too much time on editing) and then continue on and write more. Then at the end of the ten minutes have them do a final word count.
The idea behind this is that students often have trouble transferring what they want to say from their brains to the paper. By writing in steps, they are ‘priming’ themselves, and you should find that students will write more than 3x the original word count in the second step, and more than 10x the original word count in the final step. The whole process takes about 20 minutes, but it will be encouraging for your students to see just how much they can write!
Source: Martina Bex via Betsy Paskvan, Lesson Plans for CI/TPRS Classrooms