This practitioner inquiry dissertation is situated within the context of U.S. education policy that persists in defining literacy as print-based and privileges standardized literacy assessments as the singular measure of what students "know". Decades of literacy research have shown that such orientations to education policy and resulting curriculum and pedagogical practices position students from non-dominant backgrounds, including multilingual learners, as "at-risk", "remedial", and "struggling". Through this research, I implement asset-based curriculum, pedagogy, and assessment with students in a 2nd grade English as a Second Language (ESL) writing classroom. Specifically, I explore how students engaged with the end-of-school-year writing portfolio unit where they collaborated with their peers to design writing portfolios comprising writings and illustrations from the school year. Students collaboratively reflected on and revised their writing portfolio's contents and ultimately shared them with their classmates, families, and me, their ESL teacher, during student-led portfolio conferences. Writing portfolios have long been identified as an alternative assessment for multilingual learners, yet few studies exist on what emerges when teachers and multilingual students collaboratively engage in writing portfolio design, reflection, revision, and sharing. I apply posthuman orientations toward literacy, specifically drawing from multiliteracies and embodied/affective literacies to analyze the entangled material and discursive ways that students knew/became/did literacies across the writing portfolio unit. Findings show that multilingual learners have a wealth of multiliterate and affective resources that they draw upon as engage in literacy events. Further, when writing portfolios are approached as an assemblage, students come to see themselves and their literacies as "becoming". This research has implications for policy, research, and practice by demonstrating how the mapping of the multiliterate and affective flows among multilingual learners and texts can provide insights into the complex material and discursive ways that students know/become/do literacies. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]